New Delhi: Prime Minister Manmohan Singh said on Tuesday that intelligence agencies had warned more terrorist attacks were likely, possibly on economic and religious targets as well as on nuclear installations.

Singh's comments came nearly two months after a series of bombs on commuter trains in Mumbai, India's financial hub, killed more than 200 people.

India has since been on a heightened security alert, with fears of more attacks across the country, particularly in New Delhi and Mumbai, and at airports after British police last month said they foiled a plot to bomb trans-Atlantic flights.

"Concern about the increasing activities of externally inspired and directed terrorist outfits in the country is justified," Singh told an internal security meeting.

"Intelligence agencies warn of a further intensification of violent activities," he told the meeting, attended by chief ministers of states and top federal security officials.

The attacks could be carried out by suicide bombers and also target Indian army camps and other vital installations such as nuclear plants, he said.

"Reports also suggest that terrorist modules and 'sleeper cells' exist in some of our urban areas, all of which highlight the seriousness of the threat."

Tuesday's conference aimed to discuss and fine-tune security strategies to tackle terrorism and insurgencies across the country as well as improve coordination between New Delhi and the states.

Besides terrorism, the meeting was expected to discuss the revolt against Indian rule in Jammu and Kashmir, Maoist violence in eastern, central and southern India and insurgencies in the northeast.

Indian states were not doing enough to fill up vacancies in their police forces and needed to bring "beat constables" into the work of helping pre-empt militant attacks, he said.

Singh also announced the formation of a special panel of ministers, which would include the federal interior minister and chief ministers of select states, to monitor the spread of Maoist violence and coordinate efforts to counter it.

Meanwhile, India has "completely revamped" security at its nuclear facilities following warnings of possible terror attacks, the country's national security advisor said yesterday.

"We can assure you that we have completely revamped security for nuclear establishments... The arrangements are adequate for the threats we face," security advisor M.K. Narayanan told reporters without revealing details.

India's 22 military and civilian nuclear facilities are kept behind a three-tier security system manned by soldiers and anti-aircraft weapons while the atomic cores are enclosed inside blast-proof steel-and-concrete structures.

Security was revamped after the US embassy warned last month that militants may be planning a series of blasts in the run-up to Independence Day.