As the news of LTTE chief V Prabhakaran's death trickled in from Sri Lanka, Central security agencies have sounded an alert in Tamil Nadu even as intelligence inputs suggest that cadre of the outfit who could have slipped into the country may try to create disturbance.

Security for Congress President Sonia Gandhi and her children Rahul and Priyanka was further tightened as they were already on the target of the banned LTTE. All the three were guarded by the elite, Special Protection Group.

The alert has also been sounded in neighbouring Kerala and coastal Andhra Pradesh as well to keep a watch on the movement along the coastal lines as LTTE cadre, facing the wrath of Sri Lankan army, may also make fresh attempt to slip in, official sources said.

Sources said the alert specifically asked Tamil Nadu to keep a close watch as the Gandhi family may be visiting Sriperumbudur on May 21 to observe the 18th death anniversary of former Prime Minister Rajiv Gandhi, assassinated in 1991 during the run-up to elections.

The intelligence inputs also suggest some desperate LTTE ultras may flee the war zone in the guise of refugees and land up in India.

"The possible influx of suicide bombers cannot be ruled out, especially in the wake of sympathisers who may provide them refuge here," a senior official of the home ministry said.