After a decade on the run, the suspected mastermind of the September 11 attacks, Khalid Sheikh Mohammed, was in US custody yesterday in what US officials hailed as the biggest catch so far in the global war on terror.

Arrested by plainclothes Pakistani security agents who raided a house in the central city of Rawalpindi in a pre-dawn raid on Saturday, Mohammed was branded by Washington as one of al- Qaeda leader Osama bin Laden's "most senior and significant lieutenants."

Mohammed, whose arrest is a coup for the United States in its hunt for bin Laden and its global

war on terror, was handed over to US custody and taken to an undisclosed location within hours of his arrest, a senior government source said on Sunday.

"He was handed over soon after the arrest," the source said.

It was not known whether the man described by counterterrorism experts as having been behind almost every major terror attack in the last decade had been taken to Afghanistan, a military base in Cuba where other suspected al-Qaeda are held, a US ship or flown to the United States or a third country.

The White House said Mohammed, one of three al-Qaeda suspects detained in the early morning swoop, was "a key al-

Qaeda planner and the mastermind of the September 11 attacks." Officials said the others were a Pakistani and a foreign national of Arab origin.

Analysts describe Mohammed, a Kuwaiti in his late 30s, as a pivotal figure in al-Qaeda who vetted all its recruits and who may know the whereabouts of both bin Laden and Mullah Mohammed Omar, fugitive leader of Afghanistan's former Taliban government.

"It was the work of Pakistani intelligence agencies... It is a big achievement. He is the kingpin of al-Qaeda," said Rashid Qureshi, spokesman for Pakistani President Pervez Musharraf, insisting that Pakistani security had operated without US aid.

The United States, under criticism for failing to arrest the top leaders of al-Qaeda while focusing on a possible war on Iraq, was jubilant and took credit for the arrest.

"The United States commends Pakistani and US authorities on the completion of a successful joint operation, which resulted in the detention of several al-Qaeda operatives," White House spokesman Ari Fleischer said in a statement.

President Bush views Pakistan as a key supporter in the war on terror he declared after blaming al-Qaeda for the September 11, 2001, suicide plane attacks on New York and Washington.

Mohammed was reported to have narrowly evaded capture last September when Karachi police identified him as a man hit by a police sniper in a shootout with militants that netted al-Qaeda operative Ahmed Omar Abdel Rahman, known as Binalshibh.

The United States had put a $25 million price tag on his head and

the FBI posted him on its "most wanted" list of 22 individuals in October 2001.

No information was available on the second Arab held in the weekend raid. The Pakistani was identified as Ahmed Qadoos. His family said he was arrested at about 3:30 a.m. on Saturday (2230 GMT on Friday) by armed security officials, who also took away a computer. No one else from the house was arrested.

"They shut family members in a room at gunpoint," his cousin Omar Khan told Reuters. "He is not linked with anything."

Ahmed has a wife and two children and lived with his parents. His father is a retired microbiologist who had worked for the United Nations and had lived abroad, his mother is a member of one of Pakistan's most prominent Islamic parties.

But Mohammed's arrest is key.

In June 2002, US investigators identified him as the probable mastermind behind the September 11, 2001, attacks.

He was indicted in the United States in 1996 for his alleged role in

a plot to blow up 12 American airliners over the Pacific.

"Given his key position and role, it would be very surprising if he does not know the general location of Osama bin Laden," said Husain Haqqani of the Carnegie Endowment in Washington.

"Whether he will turn them in is something we don't know," he said. "The higher you are, the more devoted you are likely to be."

Mohammed was born in Kuwait, but his family is from Baluchistan, one of two Pakistani provinces bordering Afghanistan.

He is an uncle of Ramzi Ahmed Yousef, now serving a life sentence for involvement in the 1993 bombing of New York's World Trade Center, later destroyed in the September 11 attacks.

Pakistani security agencies have been hunting al-Qaeda members with the help of US intelligence agents since the ousting of the hardline Islamic Taliban government in neighboring Afghanistan in late 2001.

Hundreds of al-Qaeda members and their Taliban allies are thought to have crossed into

Pakistan since US-led forces began hunting for them in Afghanistan after the end of Taliban rule.

Pakistani President Pervez Musharraf told Reuters last week that his security forces had arrested 480 suspected al-Qaeda.

Mohammed studied in the United States, but moved to Pakistan's northwestern city of Peshawar in the late 1980s where he and his brothers are said to have linked up with a small Arab circle that included bin Laden.

US investigators say he traveled the globe as a key al-Qaeda recruiter and coordinator.

He is suspected of involvement in the bombing of US embassies in Africa in 1998 and the attack on a US warship, the USS Cole, in Yemen in 2000.

A Pakistani newspaper linked him to the kidnapping and murder of US reporter Daniel Pearl, saying investigators believed Mohammed was the man who slit Pearl's throat in front of a video camera after the journalist disappeared in Karachi in January 2002 while investigating a story on Islamic extremists.