Afghanistan's leading human rights ­organisation is investigating claims that white phosphorus was used during a deadly battle between US forces and the Taliban last week in which scores of civilians may have died.

Nader Nadery, a senior officer at the Afghanistan Independent Human Rights Commission, said the organisation was concerned that the chemical, which can cause severe burns, might have been used in the firefight in Bala Baluk, a district in the western province of Farah.

Dr Mohammad Aref Jalali, the head of an internationally funded burns hospital in Herat, said villagers taken to hospital after the incident had "highly unusual burns" on their hands and feet that he had not seen before. "We cannot be 100% sure what type of chemical it was and we do not have the equipment here to find out. One of the women who came here told us that 22 members of her family were totally burned. She said a bomb distributed white power that caught fire and then set people's clothes alight."

US forces in Afghanistan denied they had used the chemical, and have also said claims that up to 147 civilians were killed were grossly exaggerated.

As with previous such tragedies, both sides have made wildly different claims, with the Taliban seeking to exploit ­popular fury and US officials attempting to limit the damage and blame the Taliban for allegedly using civilians as human shields.But members of the human rights department at the UN mission in Afghanistan have been appalled by witness testimony from people in the village, according to one official in Kabul who talked anonymously to the Guardian.

He said bombs were dropped after militants had quit the battlefield, which appeared to be backed up by the US air force's own daily report, which is published online. "The stories that are emerging are quite frankly horrifying," the official said. "It is quite apparent that the large bulk of casualties were called in after the initial fighting had subsided and both the troops and the Taliban had withdrawn.

"Local villagers went to the mosque to pray for peace. Shortly after evening prayers the air strikes were called in, and they continued for a couple of hours whilst the villagers were frantically calling the local governor to get him to call off the air strikes."

He said that women and children hid inside their homes while their men went on to the roofs with guns. US forces say these men were militants, but the UN official said they were simply villagers and "it is totally normal for them to have guns". Also contested is an incident immediately after the battle when people from the village took piles of corpses to the governor's compound in the provincial capital.

The UN official said their willingness to ignore the Islamic custom of organising burial within 24 hours of death showed the level of anger. A statement by US forces said insurgents forced tribal elders to parade the corpses through neighbouring villages to "incite outrage".

It said that a joint US-Afghan investigation team confirmed that "a number of civilians were killed in the course of the fighting but is unable to determine with certainty which of those causalities were Taliban fighters and which were non-combatants". Last week Afghanistan's president, Hamid Karzai, called for all air strikes in villages to be stopped, a view privately backed by many in the UN. Yesterday Barack Obama's national security adviser, Gen James Jones, ruled out such a change in policy, saying "we can't fight with one hand tied behind our back".