A powerful car bomb exploded on Friday near a military base used by Russian peacekeeping troops in Tskhinvali, the capital of the breakaway region of South Ossetia, killing at least seven and injuring three.

It was the worst act of violence since the end of the war in mid-August, and threatened a fragile peace accord in which Russia has pledged to withdraw its troops from positions in central Georgia and back to South Ossetia and Abkhazia by October 10.