Kandahar governor Asad Allah Khalid said the deaths occurred after a gun battle on Sunday night during a campaign to remove fighters from the Ghorak district in southern Kandahar province.
"We have the dead bodies," Khalid said, referring to the slain Taliban fighters. He said 44 other suspects were arrested and assault rifles and some ammunition were confiscated.
US military spokesman Colonel James Yonts confirmed that more than 40 suspected insurgents had been detained. He said some may be released after questioning.
He gave no details on casualties pending completion of the operation, which follows a spate of guerrilla-style strikes in southern provinces over the weekend.
More than 1100 people have been killed in the past six months, and US military commanders believe the violence may worsen ahead of legislative elections on 18 September.
The US military said nine other suspected insurgents were detained in a two-week operation that ended on Friday in the eastern province of Paktika.
They included "four suspected leaders and advisers of a criminal cell", arrested with "Taliban propaganda on audio tapes" and three others linked to a bomb-making cell.