Chennai: Cyclone 'Gaja' is likely to intensify into a 'severe cyclonic storm' and affect north Tamil Nadu and south Andhra Pradesh on Monday.

'Gaja', which lay around 860 km northeast of Chennai and was moving at a speed of 12 kmph, is likely to intensify, the regional weather office in Chennai said on Sunday.

A deep depression in the Bay of Bengal has intensified into a cyclonic storm and is likely to cross the north Tamil Nadu and south Andhra Pradesh coast between Cuddalore and Sriharikota.

Gales reaching 80-90 km per hour was likely over Tamil Nadu, Puducherry and Andhra Pradesh.

Speaking to reporters, Area Cyclone Warning Centre Director S Balachandran said coastal areas of north Tamil Nadu would experience moderate rainfall and heavy rainfall in isolated places from the night of November 14.

"On November 15, many places will receive moderate rainfall and isolated places will get heavy rainfall," he said.

Fishermen have been advised not to venture into the sea from November 12 and those already in deep sea have been asked to return.

The Indian meteorological department however said the storm is likely to weaken gradually while crossing towards north Tamil Nadu and south Andhra Pradesh coasts as a 'cyclonic storm' during forenoon of November 15.

Listing out measures taken to face the cyclone, Revenue Administration Commissioner K Satyagopal told reporters in Tirunelveli that medical teams were on standby in all districts.

(With inputs from PTI)