Union Home Minister P Chidambaram on Sunday termed the attempt by unknown elements to derail a passenger train in Tamil Nadu as an extremist act and hoped police would catch the culprits.

Speaking to reporters after meeting Tamil Nadu Chief Minister M Karunanidhi here on Sunday, Chidambaram said: "Along with the police, the intelligence agencies are also working to nab the culprits."

Passengers of the Rockfort Express and the Salem Express had a narrow escape when a blast, blamed on critics of Sri Lankan President Mahinda Rajapaksa, destroyed three feet of rail track in Villupuram district early on Saturday.

Chidambaram met Karunanidhi to apprise him about Rajapaksa's India visit and the agreements signed with the island nation.

He said the Indian government has agreed to provide the Sri Lankan government Rs.1,000 crore (over $200 million) to build 50,000 houses to resettle the internally displaced Tamils there.

Queried about the state welcome given to Sri Lankan Minister Douglas Devananda, declared a proclaimed offender under the Indian law, Chidambaram said the union government has no official information about the cases pending against Devananda and he came to know about the cases only from the media.