Al-Shabab fighters parade new recruits after arriving in Mogadishu, the Somali capital, in October 2010 [Reuters]

A US drone aircraft is reported to have fired upon two senior members of al-Shabab, the Islamist anti-government armed group, in Somalia last week, marking the first time a US unmanned plane has been used for such an attack inside the country.

The strike, said to have been carried out on June 23, is believed to have targeted a convoy of fighters belonging to al-Shabab, which is fighting to overthrow Somalia's weak Transitional Federal Government and impose Islamic law.

The attack was not immediately identified as a drone strike, but a senior US military official familiar with the operation told the Washington Post newspaper on Thursday that it had come from such an aircraft.

The strike would make Somalia the sixth country where the US has reportedly used drones to conduct attacks. They have also been used in Libya, Yemen, Iraq and far more extensively in Pakistan and Afghanistan.

The strike hit the convoy of fighters as it drove along the cost in Kismayo, a southern port town, the AP news agency reported. Two men were wounded, and the US official identified them as senior Shabab members.

Abdirashid Mohamed Hidig, the deputy defence minister, declined to identify who the fighters were or who carried out the attack, except to say it had been done by a "partner country".

Reflects change in US strategy

Daveed Gartenstein-Ross, a counterterrorism expert at the Foundation for the Defense of Democracies, told Al Jazeera that the attack in Somalia emphasised America's new approach to counterterrorism, which favours "surgical strikes".

Given the location of the attack, in southern Somalia, it's likely the drone was launched from Kenya, he wrote in an email. The US military uses an airfield in Manda Bay, around 300km south of the area of the strike, he wrote.

Gartenstein-Ross said the United States may begin launching more drone attacks in Somalia, but that while they may be a useful tactic, they should not be mistaken for a strategy:

"It seems that the concern underlying the attack was the two leaders' relationship to [Yemeni-American al-Qaeda cleric] Anwar al-Awlaki, which suggests that the strike served a prophylactic purpose (trying to contain a perceived threat to the homeland). But does America have a plan to stabilize Somalia, of which the drones are a part? Or will drone attacks end up a means of simply keeping a threat indefinitely at bay?"

The United States previously has launched attacks in Somalia. In 2009, a raid involving US special operations troops succeeded in killing Saleh Ali Saleh Nabhan, a Kenyan national wanted for a 2002 truck bombing at a tourist hotel in Mombasa.

Al-Shabab, which is believed to maintain links with al-Qaeda franchises, is growing stronger as it consolidates its hold on the majority of Somali territory, including more than half of the capital, Mogadishu.

"They have become somewhat emboldened of late, and, as a result, we have become more focused on inhibiting their activities," the US official told the Post. "They were planning operations outside of Somalia."

The Somali Transitional Federal Government, led by President Sharif Ahmed, relies on international funding and military support from America as well as the African Union to maintain its tenuous hold on power.