Exactly two weeks to the day since 56 were killed by suicide bombers on the London Underground and one bus, the London transport system has again been hit by four blasts.

London police chief Sir Ian Blair said the details were still sketchy at this stage: "We know that we’ve had four explosions or attempts at explosions. It is still pretty unclear as to what’s happened."

Sir Blair said: "At the moment, the casualty numbers appear to be very low in the explosions. The bombs appear to be smaller than the last occasion."

He added, however, that police were regarding it as a "serious incident".

The small blasts have meant the effective shut down of the transport system. The minor explosions were reported at Oval, Shepherd’s Bush and Warren Street Tubes, as well as on a number 26 Bus in Bethnal Green.

Large areas around the stations have been cordoned off by police, one eye witness at the Warren Street area describing how police are taking no chances.

Liz Edwards, who works near Warren Street Tube station, said: "There are police, fire engines and ambulances all around there. A guy from our office had just come back from the station and said the police were aggressively keeping people away from the station and that you could not get anywhere near it."

The small blast on the No 26 Bus was powerful enough to blast out the windows but no one was injured.

A police officer told Reuters: "The bus driver heard a bang at the back of the bus. He thought it was probably a vehicle that had hit him.

"He stopped at a nearby bus stop and saw a suspect package at the back of the bus."

The fire brigade dressed in special protective clothing before approaching the bus.

According to reports, one person has been injured at Warren Street, which was evacuated after reports of smoke coming from one of the trains. Reports also suggested the injured person may have been holding a rucksack containing the detonator.

According to witness reports, a man was seen running away after dropping one of his rucksacks on the train.

Eyewitness Andrea told the BBC "We all got off on the platform and the guy just ran and started running up the escalator. Everyone was screaming for someone to stop him. He ran past me...and he ran out of the station. In fact he left a bag on the train."

Westminster tube station, Waterloo tube station and the King’s Cross Thameslink were all closed after the incident. Reports also state that St Paul’s tube and Oxford Circus tube station have also been closed.

Numerous lines have been suspended, including the whole of the Northern Line, the Victoria Line and the Hammersmith and City Line. All overground trains are still running as is the Eurostar train to France.

Prime Minister Tony Blair has called off a press conference due to be held this afternoon with Australian leader John Howard in order to convene a crisis meeting of emergency officials and ministers.

He said "We know why these things are done. They are done to scare people," Blair told a news conference. "Fortunately in this instance there appear to have been no casualties ... We've got to react calmly."

After the London bomb attacks on 7th July, the Evangelical Alliance called for prayers for those affected. The General Director of the Evangelical Alliance in the UK, Rev Joel Edwards, "We pray earnestly for those who have suffered loss or injury today and call on God to bind up the broken hearted. I have found Psalm 46 a great comfort at this time."

The Church of England head, Rev Dr Rowan Williams previously said the following as he was with Muslim colleagues and friends on an interfaith visit to West Yorkshire: "We were one in our condemnation of this evil and in our shared sense of care and compassion for those affected in whatever way."

The Archbishop called for unity, saying "Such solidarity and common purpose is vital for us all at this time of pain and sorrow and anger."
The Church also called on people to remember God during this time, saying, "This is a time to know that God suffers with the attacked and the oppressed. That is where our concentration, our presence and our prayers must be."

The Church of Scotland also called on people to remember God in the aftermath of the 7th July bombings, saying, "This is a time to know that God suffers with the attacked and the oppressed. That is where our concentration, our presence and our prayers must be."