KABUL (Reuters) - At least six prisoners of the Taliban as well as a Taliban commander died following a U.S. air strike in Afghanistan at the weekend, according to conflicting reports which U.S. officials said they were investigating.

A Defense Department official in Washington confirmed an air strike was launched against the Taliban on Saturday. The official said on Monday reports that civilians had been killed in the attack were being investigated.

Details of the incident, near the northern city of Kunduz on Saturday, remain unclear. It follows a decision by President Barack Obama to authorise greater use of U.S. combat power against the Taliban.

Sher Aziz Kamawal, a senior police commander in northeast Afghanistan, said Janat Gul Osmani, a senior Taliban commander responsible for a series of kidnappings, was killed along with five other militants when his car was hit by an air strike in the Chardara district of Kunduz.

In retaliation, he said on Monday, the Taliban killed six civilian prisoners by blowing them up.

Taliban spokesman Zabihullah Mujahid confirmed that Mullah Janat and four fighters had been killed in the air strike, which he said also killed six captured Afghan soldiers the Taliban was holding. He denied the Taliban had killed the captives itself.

“Our enemy later on spread rumours that the Mujahideen blew up and killed the prisoners which we strongly reject,” he said in a statement.

The incident comes amid a spate of kidnappings around Kunduz, with at least 200 people abducted by the Taliban on the roads near the city.

Last year, a U.S. air strike on a hospital in Kunduz run by aid group Medecins Sans Frontieres killed 42 people, in an incident an official U.S. report said was caused by a mixture of human and technical errors.