Attacks on the transport system were designed to scare people, and police hoped London will return to normal quickly, British Prime Minister Tony Blair said on Thursday.

"We have to react calmly and continue with our business. We know why these things are done - they are done to scare people and make them feel worried." Blair said at a news conference with visiting Australian Prime Minister John Howard, who arrived in London for an official visit on 20-24 July.

"Fortunately, in this instance, there appear to have been no casualties ... We've got to react calmly." said he.

Blair said terrorism will only be defeated by "going after the ideas of these people... taking them on and defeating them."

Blair also thanked Howard and the Australian people for their support since London terrorist attacks on 7 July, which left 56 people dead, and more that 700 other injured.

There have been a series of four incidents on the London transport network on Thursday. The emergency services are in attendance.

The incidents took place at Warren Street and Oval tubes, an area above ground at Shepherds Bush, and a number 26 bus, en route from Waterloo to Hackney.

Metropolitan Police Commissioner Ian Blair said earlier, "We know that we have four explosions, four attempts at explosions, and it's still pretty unclear as to what's happened."

He said the bombs appeared to be small and the situation was coming under control, and that the attacks were "close to simultaneous."

Source: Xinhua