LONDON — Brothers arrested in Pakistan and England emerged Saturday as key figures in a suspected plot to destroy U.S.-bound aircraft during flight, while prominent Muslims in Britain accused the government of encouraging extremism through its foreign policy.

Pakistani intelligence agents were questioning at least 17 people, including British nationals, officials said. British police released one suspect Friday night but were continuing to question 23 others suspected of involvement to bring down as many as 10 airliners with innocent-looking liquid explosives.

A senior Pakistani security official said the arrest of Rashid Rauf, a British citizen, was followed within days by a telephone call from someone in Pakistan urging the British plotters to execute their plan.

"This telephone call intercept in Karachi and the arrest of Rashid Rauf helped a lot to foil the terror plan," said the official, speaking on condition of anonymity.

Pakistan's Foreign Ministry said Friday that Rauf was a "key person" in the investigation. His brother, Tayib Rauf, 22, was among the suspects arrested in Britain; police refused to comment on news reports that another brother was also detained.

The Pakistani official told The Associated Press that most of those linked to the plot in Pakistan had been arrested.

Among the two or three still at large, he said, was Matiur Rahman, a senior figure in the al-Qaida-linked Pakistani militant group, Lashkar-e-Jhangvi, whose name was mentioned by one of the detainees during interrogation.

Rahman is wanted in Pakistan in connection with sectarian attacks on minority Shiite Muslims in Pakistan, in two failed attempts on the life of Pakistani President Gen. Pervez Musharraf in December 2003, and attacks in Karachi against Westerners, the official said. Rahman is believed to have met with some al-Qaida operatives in recent years, he added.

Interior Minister Aftab Khan Sherpao on Saturday refused to share any information about Rahman's possible links to the failed London terror plot.

Prominent British Muslims, including three members of Parliament, cited in an open letter Saturday "current British government policy risks putting civilians at increased risk both in the U.K. and abroad."

The letter, printed in several British papers, said Britain's intervention in Iraq and the failure to secure an immediate cease-fire between Israel and Hezbollah militants in Lebanon were providing "ammunition to extremists who threaten us all."

The British government released the names of 19 of the 24 arrested in Britain — many apparently British Muslims of Pakistani ancestry — and froze their assets.

The record of financial transactions, along with telephone and computer records, may help investigators trace more people in the alleged plot.

Britain kept its threat assessment level at "critical," indicative of an imminent attack.

The alleged plot called for the attackers to assemble their bombs aboard the aircraft, apparently with a peroxide-based solution disguised as beverages or other harmless-seeming items, and using such electronic equipment as a disposable camera or a music player as a detonator, two U.S. law enforcement officials told The Associated Press.

A U.S. intelligence official said they planned to deploy a couple of attackers per plane, and the two dozen plotters didn't all know one another — a typical security measure in terror groups.