Afghan attacks kill six Americans as Dempsey arrives

(CNN) -- An attack on a military convoy in southern Afghanistan killed three U.S. service members and two American civilians Saturday as a top U.S. military official arrived to assess the country's security, officials said.

Meanwhile, another U.S. service member was killed in a separate attack, a U.S. official said.

The deadlier attack, killing a total of five Americans, occurred in a bombing in the Zabul province, according to U.S. officials.

U.S. Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey arrived at Bagram Airfield on Saturday for meetings with coalition and Afghan leaders, the Defense Department said.

Dempsey will be apprised of an ongoing military transition where Afghan security forces are taking greater control of their country.

He will meet with Marine Corps Gen. Joseph F. Dunford, who took command of NATO's ISAF about two months ago.

"One of the things I'm going to ask , is ... what have you learned. If he tells me 'Nothing,' I'm going to say, 'Maybe we got the wrong guy,'" Dempsey told the American Forces Press Service.

His other meetings will be with Army Gen. Lloyd Austin, commander of U.S. Central Command; U.S. Ambassador to Afghanistan James B. Cunningham; and Dempsey's Afghan counterpart, Army Gen. Sher Mohammad Karimi, the Defense Department said.