The death of a major Al Qaeda leader in a daring helicopter assault in Somalia caps more than a decade-long hunt by U.S. authorities and strikes a blow to the terror group's operation there that also could trigger a new spate of attacks on Western targets.

Senior U.S. officials and other experts said the commando raid Monday afternoon left six dead, including Saleh Ali Saleh Nabhan, one of the most wanted Al Qaeda operatives in the region. Saleh's body and those of at least three other foreign fighters were taken away by U.S. special operations forces for forensic testing, after the raid in a southern village near Barawe, the officials said.

American authorities have been quiet about the brazen daylight commando attack launched from U.S. warships off the Somali coast, and the officials would speak about it only on condition of anonymity. Others hailed it as both a military and psychological success.

"It scares the bejesus out of people," said Jack Cloonan, a counterterror expert who was a member of the FBI's Usama bin Laden unit. "It reinforces the resolve that we have as a country and sends a message to young jihadists and anybody who might be thinking about taking up the cause ... that we have a long reach and a long memory."

That stark memory reaches back 11 years, to the 1998 bombings at U.S. embassies in Kenya and Tanzania that killed more than 250 people.

With Saleh's death, two Al Qaeda leaders in Somalia linked to the bombing have now been killed.

One more primary U.S. target, Fazul Abdullah Mohammed, is still believed to be in the country, with a $5 million bounty on his head. Mohammed was indicted for the 1998 bombings and has been on the FBI's list of most wanted terrorists since its inception. Mohammed has repeatedly eluded authorities' efforts to kill or capture him and is reported to be Al Qaeda's leading figure in east Africa.

But with Saleh's killing, "a very high level Al Qaeda guy in Somalia has been taken out," said Democratic Rep. Adam Smith, chairman of the House of Representatives Armed Services terrorism subcommittee. "We've had concerns about the degree to which Al Qaeda was trying to do training and maybe plan operations out of Somalia, and this will unquestionably undermine their efforts to do that."

U.S. officials have become increasingly concerned that battle-hardened Al Qaeda insurgents are moving out of havens along the Pakistan-Afghanistan border and into havens such as Somalia, where the vast ungoverned spaces give them free rein to train and mobilize recruits.

Bin Laden has urged Somalis to overthrow their new moderate Islamist president and to support their activist "brothers" in Afghanistan, Pakistan, the Palestinian territories and Iraq. U.S. officials worry that the Somalia-based al-Shabab, which the U.S. State Department has designated a terror organization, has growing ties to Al Qaeda.

The Obama administration, meanwhile, has said it wants to bolster efforts to support Somalia's embattled government by providing additional money for weapons and helping the military in neighboring Djibouti train Somali forces.

Interest in Saleh, a 30-year-old Kenyan, intensified in 2002, when he was linked to the attempted downing of an Israeli airliner and the nearly simultaneous car bombing at a beach resort in Kenya. The missile missed the plane, but 10 Kenyans and three Israelis were killed in the hotel blast.

Several attempts targeting him have failed, including one in March 2008, when the U.S. Navy fired two Tomahawk missiles from a submarine into a southern Somali town.

Saleh's death, while an intelligence and logistical coup, still leaves a stubborn insurgency in Somalia that has threatened to target U.S. and other Western interests, and raised new warnings of vengeance in the aftermath of Saleh's killing. One official who was briefed on the operation said the United States cannot underestimate the number of Somalis with links to Al Qaeda who continue to train there.

"In the overall scheme of things, this guy being taken out doesn't necessarily lessen the impact of what Al Qaeda might be doing in the Horn of Africa," said Cloonan, who helped investigate the embassy bombings. But, he added, "with him being on the most wanted list for all these years, it gives a lot of (U.S.) people a sense of a job well done that he's been taken out."

In the coming days, U.S. authorities also will watch closely to see if the attack triggers anti-American sentiment in an ungoverned country still haunted by the disastrous Blackhawk debacle of 1992, when American peacekeepers were pinned down under fire from militants and briefly overrun, leading to the deaths of 18 U.S. troops.

The use of a helicopter attack rather than a missile strike from sea or an unmanned Predator drone suggests that the United States wanted to prevent any collateral deaths to minimize such local anger. At the same time, it allowed the military to collect the bodies as evidence, which could enrage further insurgents who were deprived of the ability to complete their sacred charge and bury their dead.

U.S. officials on Tuesday described a long, patient wait for the right opportunity to hit Saleh this time. When the moment came, it involved Army and Navy forces, including elite SEALs in Army assault helicopters.

Officials said they are still working to determine who else was killed in the attack, but one official said it appears that one was Somali and others were foreign fighters of unknown origin.