Somali officials say an air strike has killed four al-Qaida-linked al-Shabab militants in southern Somalia.

The officials said an al-Shabab commander was among those killed early Friday when a missile from an unspecified plane struck a vehicle in Somalia's Lower Shabelle region. They said those killed were thought to be foreign fighters.

The strike comes one day after world leaders gathering in London pledged to help Somalia defeat terrorism and bring stability to the war-torn Horn of African country.

Al-Shabab is fighting Somalia's weak transitional government in an attempt to impose its strict version of Islamic law on the country.

Al-Shabab rebels control large portions of southern and central Somalia, but have recently lost ground in the face of offensives by Ethiopian, Kenyan, and African Union troops.

Earlier this month, al-Qaida announced a formal alliance with al-Shabab, though the groups are thought to have had informal ties for several years.