GHAZNI Afghanistan (Reuters) - Afghan villagers hanged four captured Taliban militants from a tree on Saturday as security forces battled the insurgents for a sixth day in a district of Ghazni province, an official said.

The hangings were carried out after Taliban fighters had killed more than 100 people in the area in the past week, including more than a dozen who were beheaded, according to Ghazni deputy governor Mohammad Ali Ahmadi.

The battle in the Ajrestan district of Ghazni, southwest of the capital Kabul, is part of an escalation of Taliban attacks around the country as the militants take advantage of dwindling U.S. air support as foreign forces leave.

The assault by an estimated 700 Taliban fighters began about six days ago but Afghan army commando reinforcements and the threat of NATO air strikes have so far prevented the district from falling under Taliban control, said Ahmadi.

Heavy fighting continued on Saturday in Ajrestan, in the far west of the province.

The four captured militants were handed over to residents in Arzakai village, according to Ahmadi, who also uses the name Ahmadullah Ahmadi. It was unclear who handed the men over to the villagers, or why.

Army commandos supported by aircraft from the U.S.-led military coalition arrived on Friday to help local army and police, Ahmadi said.

"Coalition jets were in the air, but they did not bombard the area because of fears of civilian casualties," he said.

Foreign forces' air support will end entirely after international combat troops leave Afghanistan at the end of the year.

The withdrawal will end a mission that began with the 2001 ouster of the Taliban former government, which applied a harsh interpretation of Islamic law, after it refused to hand over Osama bin Laden after the 9/11 attacks on the United States.

The Taliban insurgents have recently also been emboldened by months of political turmoil after a disputed presidential election, which demoralized security forces.

The election crisis ended with a power-sharing deal that will see winner Ashraf Ghani sworn in as president Monday, with runner-up Abdullah Abdullah expected to be named to a position with powers similar to those of a prime minister.

(Reporting by Mustafa Andalib; Writing by Kay Johnson; Editing by Pravin Char)