A previously unknown group calling itself "The Secret Organization of al Qaeda in Europe," has claimed responsibility for Thursday morning's blasts in London.

In a statement published on a website popular with Islamic extremists, the group says the attacks were in retaliation for Britain's involvement in Iraq and Afghanistan.

The group also threatens further attacks in Italy and Denmark "if they do not withdraw their troops from Iraq and Afghanistan."

"The time has come for vengeance against the Zionist crusader government of Britain in response to the massacres Britain committed in Iraq and Afghanistan," said the statement, published by Der Spiegel magazine in Berlin, and translated by The Associated Press in Cairo.

"The heroic mujahedeen carried out a blessed attack in London, and now Britain is burning with fear and terror, from north to south, east to west," the statement said.

"We warned the British government repeated(ly). We have carried out our promise and carried out a military attack in Britain after great efforts by the heroic mujahedeen over a long period to ensure its success."

David Harris, the former chief of strategic planning for CSIS, says the claim must be taken with a grain of salt.

"Self-identifying people taking responsibility, it's a very, very unreliable kind of thing," he told CTV. "The website concerned is known to be somewhat reliable, but still, it incorporates all of the doubts and risks that relying on any website information would do."

British police say they are treating the attacks as a terrorist incident but are keeping an open mind as to who was responsible.

"We have received no claim in terms of who was responsible and so at this time we wouldn't speculate," Brian Paddick, deputy assistant commissioner of the Metropolitan Police, told a news conference.

Kyle Olsen, a terrorism expert in Washington believes that the London attacks came from an al Qaeda-linked group.

"Certainly, it has all the hallmarks of an al-Qaeda-style attack," he told Canada AM.

"Now, whether this is al Qaeda, the Osama bin Laden organization, or one of the many franchise organizations that have sprung up across Europe pledging allegiance and trying to emulate his techniques as we saw in Madrid, that's certainly unknown at this time. But certainly it has all the right fingerprints."

The attacks bear strong similarities to the string of bombings that hit commuter trains in Madrid in March 2004, killing 191 people.

Both were attacks on major transportation systems carried out at the height of rush hour. Both involved a series of orchestrated explosions in quick sequence, apparently using bombs hidden across the system.

Al Qaeda claimed responsibility for the Madrid strikes, saying they came in retaliation for Spain's role in Iraq.

Al Qaeda also used coordinated, near-simultaneous attacks in the 1998 bombings of two U.S. embassies in East Africa and of course, in the Sept. 11, 2001, attacks on the United States.

Chuck Pena from the CATO Institute says many anti-terrorist experts have long predicted that it was only a matter of time before an attack was brought against the UK for its involvement in Iraq.

"I hate to say this, but it doesn't come as any great surprise that Great Britain would be targeted. After all, al Qaeda had said quite specifically, bin Laden has said that nations that supported the United States in Iraq would be targeted," he told CTV.

"All the countries that supported the U.S. decision to invade Iraq are clearly in the crosshairs for al Qaeda or any radical Islamic organization that buys into al Qaeda's ideology."

Pena says if those responsible are really from an al Qaeda spin-off group, it will further bolster Osama bin Laden's cause.

"From bin Laden's perspective, it doesn't get any better than this, because he and the core al-Qaeda leadership no longer have to be responsible for planning, financing, coordinating and recruiting terrorists to attack," he says.

"They know that there are plenty of Muslims out there who are listening to their words and more than willing to take up a call to arms without having any direct connection or communication."

Olsen notes that these splinter groups may be trying to prove to bin Laden their loyalty.

"There is something of an incentive for these branch or spin-off organizations to stage spectacular events of this kind, something that echoes a 9/11-style attack to establish their own credibility."