ISLAMABAD, PAKISTAN - A suicide bomber has detonated his explosives-packed vehicle outside a provincial police headquarters in central Afghanistan, killing at least 15 people and wounding more than 50 others.

Afghan officials condemned Sunday's attack in Firozkoh, the capital of Ghor province, as an act of terrorism, saying mostly civilians were among the victims. The powerful blast also damaged nearby government offices, they said.

Mohammad Omer Lalzad, the head of the provincial hospital, told VOA that "a number of injured people are in critical condition." Lalzad said he expected the death toll to rise.

No group has claimed responsibility, although the Afghan Interior Ministry blamed Taliban insurgents.

The acting U.S. ambassador to Afghanistan condemned the attack.

"Innocent Afghans were again killed today through a senseless bombing in #FerozKoh in #Ghor province. This destruction and bloodshed must stop. Afghans deserve to live their lives in peace," Ross Wilson tweeted.

Deal violations

Meanwhile, the insurgent group Sunday accused the U.S. military of violating a February peace deal between the two sides by carrying out "excessive airstrikes" in Taliban-held areas in southern Helmand province and elsewhere in the country.

Muhammad Yousuf Ahmadi, a spokesman for the Islamist Taliban, said the agreement signed in Doha, Qatar, Feb. 29 prohibits American forces from launching airstrikes in areas other than combat zones or during active fighting.

"All contents of the U.S.-Islamic Emirate [Taliban] agreement are unambiguous, but the opposite side has violated its commitments on numerous occasions, are engaging in provocative actions and bombing non-combat zones," Ahmadi said.

"We categorically reject the Taliban's claim the United States has violated the U.S.-Taliban Agreement. U.S. airstrikes in Helmand and (western) Farah (province) have been and continue to be solely in defense of the ANDSF as they are being attacked by the Taliban," tweeted U.S. military spokesman Col. Sonny Leggett. He was referring to the Afghan National Defense and Security Forces.

He said the strikes are consistent with the U.S.-Taliban agreement and Washington's understanding with Kabul.

"The entire world has witnessed the Taliban's offensive operations in Helmand -- attacks which injured and displaced thousands of innocent Afghan civilians. We reiterate our call for ALL SIDES to reduce the violence to allow the political process to take hold," Leggett said.

Last week, the Taliban staged large-scale offensives in Helmand, making territorial gains in and around Lashkargah, the provincial capital, and blocking roads leading into the city.

The United Nations says the fighting has displaced more than 35,000 civilians and caused about 200 casualties in the province, where the Taliban controls or influences most of the territory.

U.S. airstrikes

The U.S. military said last Monday it had carried out airstrikes against Taliban positions in support of Afghan security forces to repel insurgent advances in Helmand.

Gen. Scott Miller, the commander of U.S. forces in Afghanistan, defended the action, saying it was in line with the terms of the February deal. He urged the Taliban to reduce the levels of violence in the country.

The allegations and counter allegations threaten to derail peace negotiations between the Taliban and representatives of the Afghan government under way in Doha, Qatar.

The direct intra-Afghan peace talks, which stemmed from the U.S.-Taliban accord, are aimed at finding a political power-sharing arrangement among Afghan rivals to end the country's 19-year-old war and pave the way for the complete withdrawal of American and coalition forces from Afghanistan by May 2021.

On Thursday, U.S. special envoy for Afghanistan Zalmay Khalilzad said his delegation and the Taliban had agreed to take steps to reduce the violence in keeping with their peace agreement. Khalilzad did not share future details but expected the violence to go down in coming days.