11:50 PM: Condemnation by UN Secy-Gen

UN Secretary-General Antonio Guterres on Wednesday condemned the suicide bombing attack outside a polling station during Pakistan's national elections.

A suicide bomber on a motorcycle rammed into people waiting outside a polling station in the city of Quetta, killing 31 people after the polls there opened. The attack underscored the difficulties Pakistan faces on its journey toward sustained democracy.

UN spokesman Stephane Dujarric says: "The United Nations stands in solidarity with and supports the efforts of the government of Pakistan in the fight against terrorism."

6:20 PM: Imran Khan's vote could be disqualified

The spokesman for Pakistan's Election Commission says the commission has issued a notice to aspiring prime minister Imran Khan saying his vote could be disqualified after he cast his ballot in front of television cameras, violating "the secrecy of the ballot paper."

Nadeem Qasim tells The Associated Press that a notice was issued to Khan after he marked his ballot in front of TV and still cameras in violation of Pakistan's constitution, which guarantees the secrecy of the ballot. Images show a smiling Khan with his ballot paper laid out in front of him as he marks the ballot. Several cameras crowded the former cricket star turned politician.

6:05 PM: Voting ends after suicide bombing

Polls have closed across Pakistan in the national election of a third straight civilian government in the Islamic nation.

The voting ended after a suicide bombing outside a polling station in the southwest, in which 31 people were killed. However, the balloting for a National Assembly, lower house of parliament and four provincial assemblies were largely peaceful elsewhere.

Pakistan's military, at the request of the country's elections oversight body, deployed over 370,000 security forces at polling stations.

A suicide bomber on a motorcycle rammed into people waiting outside a polling station in the city of Quetta, killing 31 people after the polls there opened. The attack underscored the difficulties Pakistan faces on its wobbly journey toward sustained democracy.

5:15 PM: Nawaz Sharif requests extension of voting by an hour

A top contender in Pakistan's national elections, the party of former jailed Prime Minister Nawaz Sharif, has asked the elections oversight body to extend voting for one hour to allow people waiting to vote to cast their ballots.

Mushahid Hussain, the Pakistan Muslim League spokesman, says many of their supporters are still standing in long lines at polling stations, waiting to vote on Wednesday.

He accused election officials of taking too much time in issuing ballot papers to voters.

It's unlikely the election commission will accept the request, which came less than an hour before polls were to close.

Pakistani law allows all who enter polling stations before voting ends to cast ballots.

3:55 PM: EU observer mission chief condemns suicide bombing

The head of the European Union's observer mission in Pakistan has condemned the bombing outside a polling station in Quetta, the capital of Baluchistan province, that killed 31 people.

Michael Gahler says 120 EU observers are at 40 polling stations throughout the country as the nation votes but not in Baluchistan because of security concerns.

He says the monitors also watched as election workers prepared to start the vote on Wednesday, readying ballots and electoral rolls.

Gahler will present a preliminary report assessing elections on Friday. He says observers will look into some reports that media access was restricted by military posted at polling stations throughout the country.

2:45 PM: Sharif's and Khan's supporters clash

Police in Pakistan say more clashes between rival political parties have killed another person and wounded 15 across the country.

Officer Nasir Ahmed says supporters of the Pakistan Muslim League and Tahrik-e-Insaf parties clashed during the polling on Wednesday in the city of Khanewal, in Punjab province, firing shots and hurling clubs and stones at each other.

Ahmed says four people were taken to hospital with bullet wounds and one of them died. He said 12 people were arrested.

Supporters of the two political parties also clashed elsewhere in Punjab, injuring over a dozen people. There were also skirmishes among political activists in various towns in southern Sindh province but no casualties were reported there.

Earlier in the day, shooting between supporters of two rival parties left one person dead and wounded two in a village near the northwestern city of Swabi.

1:50 PM: Imran Khan, Bilawal Bhutto cast votes

Pakistan's opposition leader Imran Khan, who aspires to be the country's next prime minister, has cast his ballot near his suburban home in the capital, Islamabad.

Khan voted as elections got underway in Pakistan where the nation is electing a new National Assembly, the lower house of parliament, and four provincial assemblies on Wednesday.

Earlier in the day, an explosion outside a crowded polling station in the southwestern city of Quetta killed 25 people and wounded 40.

Another prominent candidate in the elections — late Prime minister Benazir Bhutto's son Bilawal Bhutto Zardari — also cast his vote, in his native town of Larkana.

Khan, who heads Tehrik-e-Insaf, or Justice Party, is likely to do well in the elections. He arrived at the polling station to warm greetings from supporters who showered his vehicle with rose petals.

After voting, Khan appealed on Pakistanis to come out in large numbers and vote sensibly "to save future generations."

The young Zardari, who is now heading her slain mother's Pakistan People's Party, condemned the bombing in Quetta.

11:45 AM: Explosion outside polling station

A Pakistan hospital official says an explosion outside a crowded polling station in the southwestern city of Quetta has killed 25 people and wounded 40. Jaffer Kakar, a doctor, says five policemen and two children are among the dead. He fears the death toll could rise as many of the wounded are in critical condition.

Wednesday's attack comes as Pakistanis vote in general elections for 270 members of the law-making National Assembly, or lower house of parliament, and 577 seats in four provincial assemblies.

No group immediately claimed responsibility for the explosion.

Abdur Razzaq Cheema, the police chief in Quetta, Baluchistan's provincial capital, says the explosion took place when near the city's eastern bypass.

Baluchistan also saw the deadliest suicide bombing in the run-up to election day, with 149 people, including a provincial assembly candidate, killed at a campaign this month.

10:40 AM: First violence on election day in Pakistan claim hundreds of lives

Pakistani police say a shooting between supporters of two opposing political parties has left one person dead and wounded two people in a village near the northwestern city of Swabi.

It is the first violence on election day in Pakistan. Ahead of Wednesday's balloting, over 170 people — including three candidates running in the elections — were killed in suicide bombings in southwestern Baluchistan and northwestern Khyber Pakhtunkhwa provinces.

Police officer Khalid Hamdani says it's unclear what triggered the shootout between a group of supporters of the secular Awami National Party, which has often been targeted by the Taliban, and the Tehrik-e-Insaf led by former cricket star Imran Khan, a centre-right party.

Hamdani says the situation is now under control and voting is underway in Col Sher Khan village.

10:15 AM: Influential maulana votes

A hard-line Pakistani cleric who heads an alliance of religious parties and the country's parliament speaker have cast their ballots in the general elections underway in Pakistan.

Maulana Fazlur Rehman voted in the northwestern city of Dera Ismail Khan soon after polls opened on Wednesday.

His Muttahida Majlis-e-Amal is a potential threat to the opposition leader, former cricket star Imran Khan's party in northwestern Khyber Pakhtunkhwa province. Khan's party has ruled the province for the last five years.

Rehman appealed to citizens after casting his ballot to cast their votes with the full sense of responsibility so capable hands could take over the country.

Ayaz Sadiq, the speaker of the National Assembly, voted in the eastern city of Lahore.

8:40 AM: Younger Sharif stands in a queue

Pakistan Muslim League chief Shahbaz Sharif cast his vote in the eastern city of Lahore soon after polls opened in national elections.

Sharif, the younger brother of disgraced ex-prime minister Nawaz Sharif, took over the ruling Pakistan Muslim League last year after his brother was found guilty of corruption. The ex-prime minister has since been sentenced to 10 years in jail, which he is serving while appealing the conviction.

The younger Sharif stood in line waiting his turn to enter the polling booth. In Pakistan, a candidate can run for elections in multiple seats. If the candidate wins more than one seat, a by-election will be held as a person can represent only one constituency.

Sharif marked his ballot for both the National and Punjab provincial Parliaments and is contesting elections in four National Assembly seats and in two Punjab provincial legislature seats.

8 AM: More than 11,000 candidates vying for 270 seats in Parliament

Pakistanis began voting in a historic third straight election ending a campaign marred by widespread allegations of manipulation that local and international rights group say imperils the country's wobbly transition to democratic rule.

There are 85,307 polling stations across Pakistan and more than 11,000 candidates are vying for 270 seats in parliament and 570 seats in four provincial assemblies. Voting for two parliament seats and six seats in provincial assemblies has been postponed for a later date, due to attacks on candidates or disqualifications. One candidate in the Sindh provincial assembly was unopposed and has already secured that seat.

Under Pakistani law, separate seats are reserved for women and for non-Muslim minorities, who comprise 4% of the population.