Fierce fighting between Taliban rebels and Afghan security forces left 18 insurgents and three others dead, a day after the U.S. military pounded suspected rebels in air strikes that killed as many as 20, officials said Monday. Three U.S. troops were slightly wounded when a bomb exploded near their armored Humvee in Paktia province on Sunday, The Associated Press quoted U.S. military spokesman Col. James Yonts as saying. A Taliban spokesman, meanwhile, claimed his fighters had assassinated a kidnapped Afghan police chief and five of his men for collaborating with the U.S.-led coalition.