The Pentagon on Tuesday said 12 militants of al-Shabaab, an al-Qaida-affiliated group in Somalia, were killed in US airstrikes this week.The US military conducted two airstrikes late Monday evening and early Tuesday morning on an al-Shabaab camp in southern Somalia due to an "imminent threat" against US troops in Somalia, Xinhua quoted Pentagon spokesman Jeff Davis as saying.Further details about the strikes were not available at the moment.Despite its involvement in assisting the Somalian government and African Union forces in battling al-Shabaab, an extremist group responsible for dozens of terror attacks in east Africa, particularly Kenya, the US military so far was not launching regular airstrikes against the group in Somalia.In March, the US military conducted an airstrike against a training camp of the group about 193 km north of Mogadishu, the largest city in Somalia, killing about 150 al-Shabaab fighters.