Sirens sounded in India's financial capital at 6.25pm (1255 GMT) - the time of the first of the seven explosions last Tuesday - bringing traffic to a stop.

President APJ Abdul Kalam, his hand raised to his forehead in salute, led the tribute as people lit candles and laid wreaths at the Mahim station, one of the seven places on hit by the bombs.

Thousands of people placed bunches of roses and tulips at the blast sites on the busy commuter network.

Bollywood stars led a silent march of hundreds of people condemning the attacks and one of the most famous male stars, Shahrukh Khan, appeared on television calling for religious unity.

"Terrorism will never succeed," read one of the banners in the silent march. "Thank you all for being strong. Thank you for being united," read another.

Group claims responsibility

Hundreds of people, mostly minority Muslims, have been questioned over the attacks but no formal arrests have been made.

An Islamic group that claims it carried out the bombings has said it is planning attacks on government and historic sites in India

Mumbai's rail system was hit by
seven bomb blasts

Lashkar-e-Qahharan, in an email sent on Tuesday to an Indian television station, said it would provide audio and video proof that it carried out the attacks.

The group first took responsibility in an email sent to Aaj Tak television on Saturday, although investigators say they are still trying to verify the claim.

Lashkar said 16 people took part in the attacks and that one of them had been killed.

"All the remaining 15 mujahideens are totally safe, and celebrating the success of this mission and also preparing for the next mission," the email said.

"We also request all the Muslim brothers and sisters of India to (not) go near the main historical, governmental and the monumental places of India (especially in Delhi and Mumbai) in future," the email said. "Otherwise, they get hurt too."

Army of Terror

Lashkar-e-Qahhar, or the Army of Terror, was unknown until it claimed responsibility for the March 7 bombings in the Hindu holy city of Varanasi that killed at least 20 people.

Investigators believe the group may be a front for Lashkar-e-Tayyaba, a group based in Pakistan that has been fighting Indian rule in Jammu and Kashmir state.

Some experts have raised doubts about the credibility of the group's claim.

"We are surprised, why some media groups and peoples are disclaiming our responsibility?" the email said.

"Very soon, we will send you an audio/video tape regarding Mumbai blasts," it said.

The email was signed by a man calling himself Abu Mahaz, who identified himself as Lashkar's spokesman and the head of its "media group."