ISLAMABAD, Pakistan - Pakistan investigated reports Tuesday that a senior al Qaeda figure was among six people killed in a suspected U.S. missile strike amid anger that the attack had violated the Islamic nation's sovereignty.

Pakistan's army said it had not confirmed that Monday's strike killed al Qaeda operative Abu Khabab al-Masri, described by Washington as an expert who trained terrorists in the use of poisons and explosives.

But two Pakistani intelligence officials said they believed al-Masri had died and an American official in Washington expressed cautious optimism. The U.S. is offering a US$5 million reward for information leading to his capture.

"There is a real sense that this guy is gone," the American official said. But he cautioned that there was no material evidence yet to confirm al-Masri's death, such as a photograph of the dead man at the bomb site.

The pre-dawn strike on a border village in the South Waziristan tribal region came hours before Prime Minister Yousuf Raza Gilani met with President Bush at the White House.

There is increasing pressure from the West on the four-month-old Pakistan government to act against Taliban and al Qaeda strongholds in its frontier region with Afghanistan amid concern that peace deals have given militants more freedom to operate.

On Tuesday, suspected Islamic militants abducted about 30 police and paramilitary troops in northwestern Pakistan, a day after three intelligence agents were killed there in an ambush. A militant spokesman, Bakht Ali Khan, claimed responsibility and accused the government of not sticking to a peace accord that was reached in May.

Bush and Gilani made no mention of the missile attack when they addressed reporters on the White House lawn. They expressed common resolve to fight terrorism.

But later in an interview with CNN, Gilani said the strike was "certainly" a violation of sovereignty if the U.S. had acted unilaterally. He said he told Bush that both countries should do a better job of sharing intelligence so that Pakistan could fight extremists itself.

Gilani said an inquiry about the strike was under way.

Asked why U.S. officials were reluctant to share intelligence more fully, Gilani said, "Basically, Americans are a little impatient."

The U.S. military in neighboring Afghanistan denied it launched the missile strike. "It was not us," said 1st Lt. Nathan Perry, a spokesman for the U.S.-led coalition.

That denial would not preclude U.S. involvement. Previous such strikes inside Pakistan are believed to have been conducted by the CIA using Predator drones.

A Pakistani military intelligence official said al-Masri's wife told authorities that her husband died in the attack in South Waziristan. The woman was wounded and hospitalized, he said.

Another intelligence official said the strike killed four Egyptians and two Pakistanis. He identified one of the Egyptians as "Abu Khuba," but made clear he was referring to al-Masri.

The officials spoke to The Associated Press on condition of anonymity because they were not authorized to comment to journalists.

A local pro-Taliban militant based in Wana, the main town in South Waziristan, said that 50 to 60 militants, including some Arabs, attended funeral prayers for the six victims within hours of the strike. He said al-Masri was among the dead.

The victims were buried in a graveyard not far from the scene of the attack near Azam Warsak village, about three kilometres from the Afghan border, he said, citing other militants who attended.

The militant requested anonymity as his chief, Maulvi Nazir, had told his followers not to cooperate with journalists.

A newspaper reporter based in Wana, the main town in South Waziristan, said militants told him not to travel to the area after he sought their permission. The journalist asked not to be named as he has received threats from militants in the past for his coverage.

Al-Masri was previously reported killed in a January 2006 missile strike by a CIA Predator drone in the Pakistani tribal region of Bajaur that targeted and missed al Qaeda's No. 2 leader, Ayman al-Zawahri. Pakistani officials said then that al-Masri was among five al Qaeda militants believed killed in that attack, but bodies were never found.

The Pakistani army's spokesman, Maj. Gen. Athar Abbas, said Monday that troops were trying to reach the scene of Monday's incident to determine what happened. He was not immediately available for comment Tuesday.

The missile strike provoked immediate complaints among politicians and media in Pakistan -- underscoring public antipathy for the government's support of the U.S.-led war on terror.

The News daily newspaper described it as an "invasion of Pakistan's airspace" and questioned why Pakistan's military did not shoot down U.S. drones.

"The inescapable conclusion is that somebody in the Pakistani government decided to turn a blind eye, and decided perhaps that they would allow the drones to operate and strike at will," the editorial said.

Zahid Khan, spokesman for the Awami National Party that governs Pakistan's volatile North West Frontier Province, condemned the missile strike.

"We are against any foreign force which interferes in our country," he said. "We also condemn those people who fire missiles on us."

But he also urged foreign militants to leave Pakistan.

"If there are (militants) sitting here, they have nothing to do here. They should leave our country."