A British newspaper says a third Islamist terror cell is planning more suicide bomb attacks against London's transit system and other targets.

The Sunday Times says members of the cell are independent of the bombers involved in two attacks this month in London, but that they have "associations" with some of the suspects connected to the July 21 failed bombings.

The newspaper quotes security sources who said "specific intelligence from several sources" warned of a plot by the "third cell" to carry out multiple suicide attacks on Thursday (7/28) - one week after failed bomb attacks on London's transit system, and three weeks after the July 7 suicide bombings that killed scores of subway and bus passengers.

The Sunday Times said word of the new bomb plot prompted a decision to deploy thousands of extra police throughout the capital on Thursday. No specific threat was announced to the public at the time, but British authorities have said the security operation in London was the biggest since the World War II.