A suicide car bomber hit a police checkpoint in Afghanistan's capital Friday, killing four people, including a policeman who tried to stop him, police and witnesses said. At least four other people were wounded in the attack in western Kabul, which also killed the bomber, police chief Esmatullah Dauladzai said. "It was a suicide attack. The attacker exploded his car when a policeman tried to stop his vehicle," Dauladzai said. There were no foreigners near the area at the time of the blast, he said.