One allegedly was in charge of the terror network's activities in Pakistan's tribal regions, semiautonomous areas that the U.S. fears have become a haven for al Qaeda and Taliban fighters involved in attacks on American and NATO forces in neighboring Afghanistan.
The suspected missile strike occurred Monday in the North Waziristan tribal region, destroying a seminary and houses associated with a Taliban commander.
The presence of al Qaeda operatives added to evidence of cooperation between homegrown militants in Pakistan and Afghanistan and the largely Arab terror group. The tribal belt is considered a possible hiding place for Osama bin Laden and al Qaeda No. 2 Ayman al-Zawahri.
Several suspected missile strikes in recent days indicated the U.S. is escalating direct efforts to root out militants along the lengthy, porous Afghan-Pakistan border.
The U.S. military and the CIA operate drone aircraft believed to have carried out such strikes, including ones that killed two senior al Qaeda commanders earlier this year. In addition, a highly unusual U.S.-led ground assault that reportedly left at least 15 dead in South Waziristan earlier this month provoked strong public protests from the Pakistani government.
Three Pakistani intelligence officials identified four foreign militants killed in the Monday strike as Abu Qasim, Abu Musa, Abu Hamza and Abu Haris. The officials spoke on condition of anonymity because of their jobs' sensitivity.
Abu Haris led al Qaeda efforts in the tribal areas, while Abu Hamza led activities in Peshawar, the main northwest city, according to the intelligence officials, who said they got the details from informants and agents in the field.
An Arab diplomat based in Pakistan with responsibilities including intelligence gathering cautioned against putting too much value in the strike, regardless of who may have been killed by the missiles.
"Al Qaeda may be moving already to replace these characters who have been killed," said the diplomat, who spoke to CBS News' Farhan Bokhari Wednesday on condition of anonymity.
"Lets be clear about one thing; It is impossible to tell if one guy is head of al Qaeda operations in the tribal areas or in Peshawar... There is no single al Qaeda operation commander anywhere. If one fellow goes down another comes up. Al Qaeda is more like a tradition or a cult where one individual after another doesn't matter. I am sure, unless decimated otherwise, al Qaeda will continue even after bin Laden. No one is immortal, but causes continue, they carry on," the diplomat said.
Abu Haris' nationality had yet to be confirmed, but Abu Hamza was from Saudi Arabia, the officials said. Abu Hamza was believed to be a bomb-making expert as well. Abu Qasim was Egyptian, while Abu Musa also was Saudi, but both appeared to be lower-ranking al Qaeda members.
An army spokesman, Maj. Murad Khan, said Wednesday the military had no information about the identity or nationality of the men killed in what he called "explosions" in North Waziristan.
"We don't know who died in the explosions there," he said.
A U.S. military spokesman in Afghanistan said he had no information he could release on the subject but did not deny an American connection.
Two of the intelligence officials said Tuesday that the overall death toll from the strike rose to 20 after residents and militants pulled more bodies from the rubble.
Witnesses said two Predator drones were in the sky shortly before multiple explosions hit the seminary and houses in the village of Dande Darba Khel on Monday morning.
The targets were associated with Jalaluddin Haqqani, a veteran of the fight against Soviet troops in Afghanistan in the 1980s who American commanders now count as a dangerous foe. Haqqani is alleged to have close connections to al Qaeda and to have helped funnel foreign fighters into Afghanistan.
Haqqani and his son, Siraj, have been linked to attacks this year including an attempt to kill Afghan President Hamid Karzai and a suicide attack on a hotel in Kabul. Haqqani network operatives also plague U.S. forces in Afghanistan's eastern Khost province with ambushes and roadside bombs.
U.S. officials say the elimination of insurgent hideouts in Pakistan is critical to stemming the growing Taliban insurgency in Afghanistan. Pakistan's fledgling government has struggled to contain militancy, despite using peace talks and force.
The Pakistan army said in a statement that 11 suspected militants were killed and seven others wounded Wednesday by artillery fire in the Kuza Bandi area of the Swat Valley, another northwest region where the military has been battling insurgents.
Separately, militants fired several rockets overnight at two military camps in North Waziristan's two towns of Mir Ali and Miran Shah, but the rockets fell in open areas and caused no troop casualties, Khan, the Pakistan army spokesman, said Wednesday.
He said the troops returned fire, but they had no information about any militant casualties.