NEW YORK - An al Qaeda operative involved in the 2005 London suicide bombings who later turned police informer and testified in trials against terror suspects in Canada and Britain has been released in New York.

Mohammed Junaid Babar, 35, confessed in 2004 to setting up the camp in South Waziristan, Pakistan, and equipping it with explosives, night vision goggles and camping gear.

He told a federal judge in New York that he knew some of the militants were planning a bomb attack in Britain. A year later, four men who were trained at the camp detonated backpack bombs in the London subway, killing themselves and 52 victims.

Babar pleaded guilty to the terrorism charges and faced a possible 70 years in prison.

Court documents show that on Dec. 10, 2010 he was sentenced to time served and 10 years of probation as a reward for his co-operation. In all, he spent only four years and eight months behind bars. The U.S. government says at least 10 people were convicted because of his testimony.

After the bombings, Babar testified in four trials targeting al Qaeda militants, three of the trials in Britain and one in Canada, in the trial against Momin Khawaja, a software developer from Ottawa.

Babar was the Crown's star witness in Khawaja's trial. He had testified at the earlier trial of the Ottawa man's co-conspirators in London in 2007, and was hoping for leniency on the American charges in return for his co-operation.

In his testimony, Babar said that he first met Khawaja in Pakistan in early 2002. "Momin told me he had come to go and fight in Afghanistan," he recounted.

But Babar said Khawaja never actually crossed the Pakistan border into Afghanistan, where the Taliban were then in disarray. Instead he went back to Canada, only to make another trip to Pakistan the next year.

Khawaja is the first person ever charged under Canada's new Anti-Terrorism Act.

He was convicted of five terrorism charges for training at a remote camp in Pakistan and providing cash and other help to British terrorists. He was also found guilty of two Criminal Code offences related to building a remote-control device to set off explosions.

In 2008, Khawaja was sentenced to 10 1/2 years in jail, but two months ago, Ontario's highest court increased his sentence of to life in prison, of which he must serve 10 years before he is eligible to apply for parole -- the maximum sentence under Canada's anti-terror laws.

Babar's sentence, which was originally reported on Monday by the Guardian newspaper, prompted a fierce reaction in Britain, where a lawyer representing victims' families and survivors of the London bombings called the move "crazy."

"There is no way a reduction of this size has any regard to the feelings of victims," Clifford Tibber said Monday.

Graham Foulkes, whose 22-year-old son David was killed by one of the blasts that hit London's transport network, said Babar's co-operation with U.S. authorities does not diminish his role in the attacks.

"To be responsible for the deaths of 52 people, serve four-and-a-half years and be released and to say that means he has paid his debt to society just beggars belief," Foulkes told the U.K.'s Guardian newspaper.

Babar's defence lawyer did not immediately return a telephone call seeking comment. The U.S. attorney's office would not comment on the case.

Babar, a U.S. citizen, was arrested in 2004 on five charges of supporting al Qaeda. In a court appearance in June 2004, he told federal judge Victor Marrero that he helped set up the base in the summer of 2003 to train Taliban militants who were fighting U.S. troops in Afghanistan.

He said he delivered night vision goggles, sleeping bags, waterproof socks, rain ponchos and money to a "high ranking official" of al Qaeda who was running the camp. He also arranged shipments of aluminum nitrate, ammonium nitrate and aluminum powder for making bombs that were tested at the camp.

"I was aware that some of the people who attended the jihad training camp had ideas about, you know, plotting against some targets in the United Kingdom, and I provided some of the materials," Babar told the judge.

As part of his Dec. 10 sentencing, the judge ordered Babar to pay a $500 fine. Prosecutors agreed to enrol him in the U.S. government's witness protection program and give new identities to him and his family. Babar's plea agreement with the government bars him from striking any book deals or giving interviews to news media.

Under the terms of his release Babar must meet monthly with a probation officer and cannot travel without the government's permission. After five years he can apply to have the remaining five years of probation lifted, court documents show.

With files from The Canadian Press