How many policemen were killed in the bombing?

Iraqi security officials say a suicide car bomber struck a police checkpoint in western Ramadi today, killing at least 20 people and wounding 30 others. The top local police official said two policemen were among the dead. Ramadi is the capital of the restive al-Anbar province, which has been a stronghold of Sunni insurgency. But recently many tribes have switched sides and joined the Iraqi police and army in an attempt to expel al-Qaida in Iraq fighters from their region. Separately, reports say U. S. and Iraqi forces have moved into the southern city of Diwaniyah in an operation to stop increasing influence of Shiite militia loyal to anti-American cleric Moqtada al-Sadr.