Taliban insurgents released 235 civilians held since seizing control of an area in northern Sari Pul province five days ago, provincial officials confirmed on Wednesday.

Zabi Amani, spokesman for the provincial governor, said the civilians were released after negotiations between the Taliban and tribal elders. The insurgents were still holding an unknown number of civilians, he said.

Most of the civilians are staying in area mosques and some are with their relatives in the city and provincial officials are trying to provide them food and other necessities until finding a solution for the problem, he said.

Fifty two civilians including women and children have been killed in Mirzawalang in Sayad district since insurgents took control of the area, Amani said.

Qari Yusouf Ahmadi, a Taliban spokesman, claimed responsibility for seizing the area, but he denied that civilians were killed in Mirzawalang.

According to provincial officials, this is the first time that Taliban and militant Islamic State (IS) group fighters jointly carried out an assault. The attack left at least 52 civilians, mostly Shias and Hazaras, dead.

So far, IS hasn't commented on the attack. Villagers who were released told local media that they saw both the Taliban's white banner and the IS' black flag flying together in their village.

There have been reports of battles between the Taliban and IS affiliates in Afghanistan in various provinces, but this is the first time both groups have occupied an area together in Sari Pul province.

Soon, Afghan security forces will begin an operation to retake the Mirzawalang area, Amani said.

The insurgents defeated Afghan local police after almost two days of intense fighting and took control of the area early on August 5, Amani said.

Afghan president Ashraf Ghani condemned the killing of civilians.

“I will promise that our brave security forces will take revenge,” Ghani said during a ceremony at the presidential palace broadcast live on TV.