KABUL: A manhunt was under way Monday for Taliban militants who publicly executed a woman accused of adultery, Afghan authorities said, as outrage mounted after a video of the cold-blooded killing surfaced.

The commander of Nato's 130,000 troops in Afghanistan, General John Allen, offered to help local security forces track and capture the men involved in what he called “an atrocity of unspeakable cruelty”.

The brutal shooting of the lone woman before a cheering mob of men is shown in graphic detail in a video of the event in a village in Parwan province some 100 kilometres north of the capital Kabul.

“We have sent a police force to the area,” Parwan provincial governor Basir Salangi told AFP, adding that the government had no permanent presence in the valley.

“They are searching for the Taliban who are responsible but the Taliban, including the killer, have fled to the mountains.”

Roshna Khalid, Salangi's spokeswoman, separately told AFP the 22-year-old woman, named as Najiba, was married to a member of the hardline Islamist Taliban and was accused of adultery with a Taliban commander.

“Within one hour they decided that she was guilty and sentenced her to death. They shot her in front of villagers in her village, Qol,” she said.

Public executions of alleged adulterers were common when the Taliban regime was in power from 1996 until 2001, when they were ousted by a US-led invasion for harbouring Al Qaeda leader Osama bin Laden after the 9/11 attacks.

The Taliban have since waged an insurgency against the Western-backed government of President Hamid Karzai.

“There has been too much progress made by too many brave Afghans, especially on the part of women, for this kind of criminal behaviour to be tolerated,” Allen said.

The video also drew international condemnation, with British Foreign Secretary William Hague saying he was “shocked and disgusted” by the execution.

“Such deplorable actions underline the vital need for better protection of the rights of women and girls in Afghanistan,” he said.

US Secretary of State Hillary Clinton, before the video surfaced, made a powerful plea Sunday for the rights of women in Afghanistan, amid fears that recent gains for women are under threat as Nato troops prepare to leave in 2014.

Clinton, who was addressing a world conference in Tokyo on Afghanistan's future, said: “The United States believes strongly that no nation can achieve peace, stability and economic growth if half the population is not empowered.”

President Hamid Karzai's government condemned the killing as “un-Islamic and inhuman”, ordering police to find and bring to justice those responsible.

The video opens with the woman, wrapped in a grey shawl, sitting at the edge of a ditch in a village surrounded by dozens of men, some perched on rooftops for a better view.

As she sits with her back to the crowd a bearded man is seen reading verses from the Koran condemning adultery, before saying: “We cannot forgive her, God tells us to finish her.”

The video then shows a man in white being handed an AK-47 rifle.

Some local reports said the shooter was the woman's husband but Khalid, the governor's spokesperson, told AFP that he was a relative of the victim's husband.