ISLAMABAD, Pakistan - Pakistan seized three bomb-laden vehicles and arrested three suspected suicide attackers, uncovering the plot just days after an assault on the Danish Embassy, officials said yesterday.

Authorities ramped up security near the enclave where most diplomatic missions are located. The U.S. Embassy strongly advised Americans to limit nonessential movement in the capital and in nearby Rawalpindi.

"They [the suspects] had very destructive designs," city police chief Nasir Durrani said. "They wanted to create mayhem on a wide scale."

Durrani said authorities still were investigating whether the suspects had intended to target embassies. He did not identify them or say whether they were affiliated with al-Qaeda or any other extremist group.

An Internet posting Thursday, purportedly from al-Qaeda in Afghanistan, claimed responsibility for Monday's bombing outside the Danish Embassy in Islamabad. Six people were killed in the blast, including one Dane.

The group threatened more attacks on countries where caricatures of the prophet Muhammad are published. The images published in various Danish and other Western newspapers over the last three years have sparked periodic unrest in the Muslim world.

Police and intelligence agents late Thursday arrested about six suspects, including three would-be suicide bombers, in Rawalpindi, seven miles from Islamabad, officials said.

Authorities seized three vehicles laden with more than 2,200 pounds of explosives, Rawalpindi police said.

Durrani said that the arrested men were Pakistanis and that their targets included a Rawalpindi office of President Pervez Musharraf, a longtime U.S. ally in the war against terrorism. Pakistan's army also has its headquarters in Rawalpindi.

Authorities tightened security near the presidential palace, parliament, and key government offices. Police checked the identification papers of people entering the diplomatic enclave, causing traffic jams, witnesses said.

Sweden, whose embassy is near the Danish mission, said it had increased security in response to the arrests.

Pakistani officials said Monday's attack on the Danish Embassy was launched by a suicide attacker in a car equipped with fake diplomatic registration plates.

It was the deadliest strike against Denmark since the publication of cartoons sparked unrest in early 2006. In February this year, Danish papers reprinted a drawing of Muhammad in a bomb-shaped turban, stirring more anger.

Yesterday, Pakistani Foreign Minister Shah Mehmood Qureshi visited Afghanistan, which fears an escalation in Taliban attacks on its side of the border between the two countries. He reiterated the government's assertion that it would not cut deals with terrorists.

Air Strike Kills 20 in Afghanistan

An air strike

has killed at least 20 extremists in eastern Afghanistan's Paktika province, a U.S.-led coalition spokesman said yesterday.

Afghan officials

said coalition aircraft had attacked

a band of insurgents in Orgun, a district close to the Pakistani border where U.S. troops have a base, after dark Thursday evening.

Surviving insurgents

removed the bodies from the scene, a police chief said. He said villagers reported that 32 extremists had died.

Most of the dead

were foreign fighters, including Pakistanis and Central Asians, a spokesman for the provincial governor said.

- Associated Press