KABUL (Reuters) - The Afghan Taliban and Islamic State attacked a village in the northern province of Sar-e Pul this week, killing between 50-60 people, a leading Afghan human rights group said on Friday.

The Taliban, seeking to restore Islamic rule after their 2001 ouster, rejected statements that the attack on Mirza Olang was a joint operation with the local affiliate of Islamic State, saying they acted alone and had targeted security forces.

However the Afghanistan Independent Human Rights Commission said a preliminary investigation suggested that the two groups, which are normally bitter rivals, acted together.

“Evidence shows that this brutal crime has been committed by the Taliban in collusion with the ISIS group,” the AIHRC said in a statement, based on what it said was “extremely shocking and terrible” witness testimony.

The attack on Mirza Olang has highlighted the dire security situation in many provincial areas of Afghanistan, where the government controls no more than 60 percent of territory and where armed militant groups operate freely in many areas.

Any cooperation between the Taliban and Islamic State would cause alarm in both the Afghan government and the United States which keeps thousands of troops in a counter-terrorism mission in Afghanistan to fight groups like ISIS and al Qaeda.

Villagers who escaped Mirza Olang had previously told reporters that they saw fighters carrying both the white banner of the Taliban and the black banner of Islamic State.

But in a region where different bands of fighters often switch between different militant groups, it can be difficult to establish allegiances with any certainty.

The AIHRC report quoted witnesses as saying the attack was led by a Taliban commander called Mullah Nader and an Islamic State commander called Ghazanfar. However Ghazanfar has previously been identified by Taliban officials as one of their commanders.

The AIHRC report said between 50 and 60 people, including five women and three children, had been killed in the attack, quoting a witness who said victims’ hands were tied before they were shot. In addition, three people were beheaded.

It said the insurgents had taken the village after two days of fighting with local security forces and local militia fighters, killing cattle and destroying property.

In total 471 families had fled the village to nearby villages and the provincial capital Sar-e Pul and they required urgent humanitarian assistance, the AIHRC statement said.