A relative of Ahmed Quddus shows his drivers’ licence after his arrest in Rawalpindi on Saturday. (Reuters)

Islamabad, March 2 (Reuters): After a decade on the run, the suspected mastermind of the September 11 attacks was being interrogated by US and Pakistani agents today after what Washington called the biggest catch so far in the war on terror.

Pakistan said its agents arrested Khalid Sheikh Mohammed, described by US officials as one of al Qaida leader Osama bin Laden’s “most senior and significant lieutenants”, and two other al Qaida suspects at a house in Rawalpindi early yesterday.

Rashid Qureshi, spokesman for President Pervez Musharraf, said Mohammed was still in Pakistan being jointly questioned by Pakistani and US agents.

Earlier, a government official who did not want to be identified had said Mohammed had been handed over to US custody shortly after his arrest, along with the two other suspects.

Interior minister Faisal Saleh Hayat denied this. “Khalid Sheikh Mohammed is in the custody of Pakistan’s law enforcement agencies and until we have satisfied ourselves, after the interrogation process, of the nature of his activities in Pakistan, there is no question of handing him over to anyone,” he said. “Only when Khalid’s country approaches us and makes a formal request for his extradition, only then will the Pakistani government hand him over.”

But information minister Sheikh Rashid said he could “give no guarantee (Mohammed) still will be in Pakistan tomorrow”. Qureshi said the fate of Mohammed, born in Kuwait in 1965 of parents from Pakistan, would depend on the interrogation.

Analysts described Mohammed as a pivotal figure in al Qaida who planned its operations, vetted all its recruits and may know the whereabouts of both bin Laden and Mullah Mohammed Omar, fugitive leader of Afghanistan’s former Taliban government.

The US, under criticism for failing to arrest the top leaders of al Qaida while focusing on a possible war on Iraq, was elated by news of Mohammed’s arrest. It claimed joint credit and described Mohammed as “a key al Qaida planner and the mastermind of the September 11 attacks”.

Pakistani officials said the others held were a Pakistani and a foreigner of Arab origin. An intelligence source said the third man was an Egyptian, but gave no other details.

Information minister Rashid said on Pakistan Television that the men put up resistance. “Shots were fired but no one was injured,” he said.

But the family of the arrested Pakistani, Ahmed Quddus, said he was the only person seized when 20-25 armed security men raided their home in the Rawalpindi district of Westridge before dawn yesterday, and no shots were fired.

Relatives of the 41-year-old Quddus said today he was mentally slow and had no connection with any extremist group. “My brother has never been involved in any bad things,” said his sister, Qudsia Khanum. Quddus’ father is a retired microbiologist who once worked for the UN, while his mother is a member of one of Pakistan’s most prominent Islamic parties.

Some analysts questioned whether Mohammed had actually been arrested yesterday and speculated he might have been held for some time and the news made public when it was in the interests of the US and Pakistan.

Washington had put a $25 million price on his head. He was one of 22 people on the FBI’s list of “most wanted terrorists”.

Mohammed was indicted in the US in 1996 for his alleged role in a plot to blow up 12 American civilian airliners over the Pacific. Intelligence officials in the Philippines said he was also part of a cell accused of plotting to kill Pope John Paul in that country in 1995. He is also suspected of involvement in the bombing of US embassies in Africa in 1998 and an attack on US warship USS Cole in Yemen in 2000.

A Pakistani newspaper also linked him to the kidnapping and murder of US reporter Daniel Pearl. It said 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.

The chairman of the US House of Representatives intelligence committee, Porter Goss, said the arrest would result in “other very successful activities soon”.

Analysts said Mohammed could be vital to finding bin Laden. “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.

Mohammed 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. He studied in the US, but moved to Peshawar in the late 1980s where he and his brothers are said to have linked up with bin Laden.