Two more persons have been detained for questioning by the police in Chennai following the arrest of a suspected militant Abdul Gafur for allegedly plotting to carry out bomb attacks in Tamil Nadu on August 15.

The two, Heera alias Kasim of Tirunelveli and Abdul Khader of Mannadi in Chennai were picked up on Sunday night, on information provided by Gafur, who was held on Sunday in Tirunelveli.

"Gafur named them as his associates. A special team from Tirunelveli will be arriving in Chennai on Monday to interrogate the two," police sources said.

Gafur (39) had planned to plant bombs in Chennai and Tirunelveli as well as trains, police said, adding that the mastermind behind the conspiracy was Ali Abdullah, a member of Jihad Committee, who is serving a jail term in Puzhal prison.

Meanwhile, five persons have been arrested for circulating hoax SMSs, warning of bomb blasts in Chennai on Monday.

Police Commissioner R Sekar warned people against such activities, saying it was a non-bailable offence that could also lead to three years' imprisonment. "Even forwarding such messages is a crime," he said.

According to the police, security at places of importance has been beefed up. Chennai police, led by Sekar, is carrying out combing operations.

Railway stations, especially on suburban routes, have been brought under security cover, with metal detectors placed at some important stations.

Frequent public announcements are being made to passengers asking them to be cautious about unclaimed articles and to report the presence of any such articles to authorities.