From Washington Post:
Small explosions at three London subway stations and on a double-decker bus shut down part of the city's transportation system Thursday but caused no significant casualties or damage, and Prime Minister Tony Blair encouraged people to resume their normal activities.
London's police commissioner, Ian Blair, described the explosions as "attempts" to cause more serious damage. British news media reported that detonators had gone off, but not major bombs, possibly indicating that a terrorist attack meant to be similar to a devastating series of blasts two weeks ago had failed because of faulty explosives.