ISLAMABAD — A British suspect in an alleged plot to blow up trans-Atlantic jetliners escaped from police custody in Pakistan yesterday, officials said.

Rashid Rauf fled after appearing before a judge at a court in the capital, Islamabad, a city police official, Khalid Pervez, said.

Police teams were driving around the area in search of Mr. Rauf, who Mr. Pervez said had managed to open his handcuffs and evade two police guards who were taking him back to jail in the nearby city of Rawalpindi.

“We do not know how he escaped. But we do know he has escaped and the two policemen have been taken into custody for negligence,” Mr. Pervez said.

The federal interior secretary, Kamal Shah, said he had been informed of Mr. Rauf’s disappearance, but had no details.

Mr. Rauf, who is of Pakistani origin, was arrested here in August 2006 on a tip from British investigators. He has been described as a key suspect in a purported plot to blow up jetliners flying from Britain to America which prompted a major security alert at airports worldwide and increased restrictions on carryon items.

The British embassy in Islamabad said it was seeking an explanation. “We are urgently seeking clarification of what happened,” a spokeswoman, Laura Davies, said.

Mr. Rauf was arrested and charged in Pakistan with possessing chemicals that could be used in making explosives and with carrying forged travel documents.

The prosecution later withdrew the case against him, though he remained in jail awaiting a decision on the British extradition request.

Britain had asked Pakistan to hand him over in connection with a 2002 murder inquiry in Britain that is separate from the alleged terrorism plot. But Mr. Rauf’s lawyer, Hashmat Habib, has sought to block the move, saying the two countries do not have an extradition treaty and that Mr. Rauf had already been found innocent of involvement in terrorism.

Members of Mr. Rauf’s family have appealed to Pakistani authorities to release him, saying he is innocent and desperate to remain with his wife and two daughters.

Mr. Habib said yesterday that his client had been brought to court in connection with the extradition proceedings, but he didn’t know how Mr. Rauf had escaped.

Mr. Rauf’s father, reached in Birmingham, 200 miles north of London, said he did not know about his son’s escape.

“I don’t know anything — I’m shocked,” Abdul Rauf said.

The British government this week denied media reports that Mr. Rauf was to be extradited from Pakistan as part of a secret deal involving the arrest in Britain of suspects wanted by Pakistan.

Two men accused of inciting terrorism and murder in Pakistan and of having links with an international terrorist group were ordered held in custody in London on Tuesday.

Faiz Baluch, 25, and Hyrbyair Marri, 39 — both of London — were arrested last week and jointly charged under Britain’s Terrorism Act. Both claim they are peaceful activists calling for the independence of Baluchistan, a troubled province of Pakistan.