Afghanistan ? An Afghan soldier killed three British service members with gunfire and a rocket-propelled grenade in the dead of night, a betrayal that highlights the difficulties in rapidly building up Afghan security forces so that foreign troops can go home.

The soldier fled the base after carrying out the attack in southern Afghanistan early Tuesday, leaving his motive unclear. But the Taliban claimed that he was a militant sympathizer who was taken in by insurgents after the assault — one that could further weaken support in Britain for an unpopular war that has now taken the lives of 318 Britons.