SANAA, Yemen (AP) ― An airstrike killed al-Qaida’s No. 2 leader in Yemen along with six others traveling with him in one car on Monday, U.S. and Yemeni officials said, a major breakthrough for U.S.-backed efforts to cripple the group in the impoverished Arab nation.

Saeed al-Shihri, a Saudi national who fought in Afghanistan and spent six years in the U.S. military prison at Guantanamo Bay, was killed by a missile after leaving a house in the southern province of Hadramawt, according to Yemeni military officials.

They said the missile was believed to have been fired by a U.S.-operated, unmanned drone aircraft.

Two senior U.S. officials confirmed al-Shihri’s death but could not confirm any U.S. involvement in the airstrike. The U.S. doesn’t usually comment on such attacks although it has used drones in the past to go after al-Qaida members in Yemen, which is considered a crucial battleground with the terror network.

Yemeni military officials said that a local forensics team had identified al-Shihri’s body with the help of U.S. forensics experts on the ground. The U.S. and Yemeni military officials spoke on condition of anonymity because they weren’t authorized to release the information to the media.

Late Monday, after speculation surfaced that the attack was carried by a U.S. drone, Yemen’s Defense Ministry issued a statement saying al-Shihri and six companions were killed during an operation by Yemeni armed forces in Wadi Hadramawt, but it did not elaborate on how they were killed.

Yemeni military officials said they had believed the United States was behind the operation because their own army does not the capacity to carry out precise aerial attacks and because Yemeni intelligence gathering capabilities on al-Shihri’s movements were limited.

A brief Defense Ministry statement sent to Yemeni reporters on their mobile phones earlier in the day only said that an attack had targeted the militants. It did not specify who carried out the attack or when it took place.

Al-Shihri’s death is a major blow to al-Qaida’s Yemen branch, which is seen as the world’s most active, planning and carrying out attacks against targets on and outside U.S. territory. The nation sits on the southern tip of the Arabian Peninsula and is on the doorstep of Saudi Arabia and fellow oil-producing nations of the Gulf and lies on strategic sea routes leading to the Suez Canal.

The group formally known as Al-Qaida in the Arabian Peninsula took advantage of the political vacuum during unrest inspired by the Arab Spring last year to take control of large swaths of land in the south. But the Yemeni military has launched a broad U.S.-backed offensive and driven the militants from several towns.

After leaving Guantanamo in 2007, al-Shihri, who is believed to be in his late 30s, went through Saudi Arabia’s famous “rehabilitation” institutes, an indoctrination program that is designed to replace what authorities in Saudi Arabia see as militant ideology with religious moderation.

But he headed south to Yemen upon release and became deputy to Nasser al-Wahishi, the leader of Al-Qaida in the Arabian Peninsula. Al-Wahishi is a Yemeni who once served as Osama bin Laden’s personal aide in Afghanistan.

Al-Qaida in Yemen has been linked to several attempted attacks on U.S. targets, including the foiled Christmas Day 2009 bombing of an airliner over Detroit and explosives-laden parcels intercepted aboard cargo flights last year.

Last year, a high-profile U.S. drone strike killed U.S.-born Anwar al-Awlaki, who had been linked to the planning and execution of several attacks targeting U.S. and Western interests, including the attempt to down a Detroit-bound airliner in 2009 and the plot to bomb cargo planes in 2010.

Unlike other al-Qaida branches, the network’s militants in Yemen have gone beyond the concept of planting sleeper cells and actively sought to gain a territorial foothold in lawless areas, mainly in the south of Yemen, before they were pushed back by U.S.-backed Yemeni government forces after months of intermittent battles. The fighting has killed hundreds of Yemeni soldiers.

The Yemen-based militants have struck Western targets in the area twice in the past 12 years. In 2000, they bombed the USS Cole destroyer in Aden harbor, killing 17 sailors. Two years later, they struck a French oil tanker, also off Yemen.