(Adds another bomb in Doura) BAGHDAD, Feb 20 (Reuters) - Two car bombs killed 10 people in southern Baghdad on Tuesday, police said, as insurgents kept up the pressure despite a major U.S.-backed security crackdown aimed at stabilising the Iraqi capital. The first car bomb exploded near a fuel station in the district of Saidiya, killing five people and wounding 11 more, police said. Another police source, however, said three were killed and 12 wounded in that attack. Another car bomb exploded in Doura, in the south of Baghdad, killing five people and wounding seven at a vegetable market. Security forces foiled another car bomb attack, blowing up a vehicle near a police checkpoint in Doura, police said.