GARDEZ, Afghanistan (Reuters) - A suicide bomber detonated his explosive vest in a crowd of spectators at a volleyball match in Afghanistan on Sunday, killing 45 people, a provincial official said, as foreign troops withdraw from the country after more than a decade of fighting.

Mukhles Afghan, spokesman for the governor of Paktika province, said at least 50 more were wounded in the attack in Yahya Khel district, where residents had gathered to watch a tournament final.

He said most of the casualties were civilians.

No one immediately claimed responsibility for Sunday’s attack. The spokesman said around 50 more people were wounded.

Casualties were high because the crowd was so dense, since people had come from nearby districts to cheer on their team. No other details were immediately available because of the remoteness of the location.

The Taliban and other jihadist militants have unleashed waves of suicide attacks in Afghanistan this year as foreign forces pull out after 13 years of war.

About 12,000 international troops will remain in Afghanistan next year to train and support Afghanistan’s security forces.

Paktika was the site of one of this year’s deadliest attacks in July, when 89 people were killed by a bomb in a crowded market.

International Olympic Committee President Thomas Bach condemned the “cowardly” attack.

“It is an attack on sport itself and on the positive values it can bring to help build strong communities and foster peace and reconciliation around the world,” he said in a statement.

The Taliban banned public sports events as un-Islamic during their five-year rule before the 2001 U.S.-led intervention that toppled them from power after the Sept. 11 terrorist attacks on U.S. cities.

Paktika province has an active Afghan Taliban insurgent presence and lies along the porous border with Pakistan’s North Waziristan region, used as a base by both the Haqqani militant network and the Pakistani branch of the Taliban.

The Pakistani army for months has been waging an offensive against militants in North Waziristan, driving refugees and militant fighters across the border into Afghanistan.

This year has been one of the bloodiest for Afghan civilians, according to the United Nations, which recorded nearly 5,000 deaths and injuries of civilians in the first half of the year.