Blair: We must remain calm

LONDON - (VIDEO) London's Metropolitan Police Commissioner Ian Blair has confirmed Thursday that there were four attempted explosions in what he described as "serious incidents."

"We've had four explosions - four attempts at explosions," he told reporters outside police headquarters at Scotland Yard, adding that at the moment the casualty numbers appear to be very low and that the bombs appear to be smaller than those that rocked the three Underground stations and a bus two

weeks ago.

“What we don’t want is lots of people going to railway stations or whatever – the trains, as far as I know, are still running. Just stay where you are, go about your normal business.”

BBC has reported the bombs were made up only of detonators, and did not contain explosives.

Police were searching London's University College Hospital for a man wearing a blue shirt with wires protruding from a hole in the back, Sky News reported.

An internal memo urged staff to watch for the man, described as a black or Asian male, about 6-feet-2 (183 centimeters). Officials have also confirmed they have found no traces of chemical agents at Warren Street station.

Three explosions took place in the city's underground train system, while another bomb exploded on a bus traveling in the East End area.

So far, only one person, perhaps the bomber, has been reported wounded.

The emergency coincided with a memorial service for the attacks of July 7. Then, four young British Muslims detonated bombs in three underground trains and a bus at morning rush hour, killing more than 50 people and shocking a capital that had hitherto been spared al Qaeda-style attacks on civilians.

Those bombings confronted Britain's people and politicians with the prospect the country could be nurturing its own generation of the type of Islamist militants loyal to Osama bin Laden who had already inflicted carnage in the U..S. on Sept. 11, 2001, in Bali and on Madrid trains last year.

A source at the underground transport company said one nail bomb exploded at Warren Street underground station; moreover, men dressed in chemical protection suits are preparing to enter the station.

'We will defeat terror'

There were also unconfirmed reports of a shooting.

A spokesman at Scotland Yard police headquarters told Reuters emergency services were responding to

reports of incidents at three locations on the underground - Oval, Warren Street and Shepherd's Bush.

The Fire Brigade said Warren Street underground station was evacuated after reports that smoke was seen coming out of a train.

One man was injured at station, but the extent of his injuries are unknown.

The witness told Sky TV a passenger on a train near Warren Street underground station had told him there had been a small explosion in a passenger's rucksack.

"The rucksack was blown open by the force of a minor explosion," he said.

A television reporter at Oval underground station said police had cordoned off the area and brought in sniffer dogs.

"These attacks are done to scare people, we have to remain calm," British Prime Minister Tony Blair said  at a press conference following the second attack on London's transportation.

"Fortunately, it appears there are no casualties."

The prime minister said terrorists are driven by, "an evil, bankrupt ideology that is based on a perversion of Islam."

"I have no doubt we will defeat it," he said.

Jewish Agency envoy to London Shira Amarglick told Ynet the agency’s offices were closed immediately by security personnel and the employees were sent home.

“We were forbidden from using public transportation. Many employees hurried to pick their children up from kindergarten. I picked up my children as well; not because of a specific order to do so, but because of my personal hysteria.”

Diana Bachur-Nir contributed to this article