A bomb exploded in a market in southern Afghanistan on Friday, injuring four civilians, police said. Elsewhere in the region, a gunfight between police and suspected Taliban rebels left two officers and three militants dead. The latest violence comes a day after Afghan and American troops killed a suspected Taliban leader in their drive to secure unstable parts of Afghanistan ahead of Sept. 18 parliamentary elections, the U.S. military said Friday. A U.S. service member was killed Thursday in an explosives training accident in central Uruzgan province — the seventh American fatality in eight days.Officials have warned of a possible spike in violence ahead of the vote — the next stage in the country's efforts to build a democracy after a quarter century of conflicts. The bomb in the southern city of Kandahar was thought to have been planted in front of shoe and clothing shops that had opened for a half-day at Rangrazal market, which was officially closed for the Muslim day of prayer. Two men, a woman and a child were wounded and several shops were damaged, said Kandahar province's police chief Abdul Malik Wahidi. No suspects were arrested. It was the latest such attack in Kandahar, where a suicide bombing on June 1 killed 20 people. The victims then included a supporter of President Hamid Karzai and the police chief of the capital, Gen. Akran Khakrezwal.