Isis has beheaded 15 of its own fighters due to infighting in Afghanistan's eastern province of Nangarhar, officials say.

Attaullah Khogyani, the provincial governor’s spokesperson, said the executions occurred in the Surkh Ab bazaar of Achin district.

Nangarhar, which is on the border with Pakistan, has become a stronghold for Isis, which in June captured territory around Tora Bora, the former refuge of Osama bin Laden.

There was no confirmation of the killings from Isis, whose local branch is known as Islamic State in Khorasan, an old name for the area that includes modern Afghanistan.

In separate violence, a suicide attack on Thursday tore into a crowd in Jalalabad, the provincial capital, killing at least eight.

The two incidents underline the insecurity and lawlessness across Afghanistan, where thousands of civilians have been killed or wounded this year amid unrelenting violence involving militant groups including Isis and the Taliban.

Footage shows the Syrian military approaching the final Isis stronghold in Syria

In a bloody day for the province, a suicide bomber blew himself up at a meeting of supporters of a police commander who was sacked for illegal land appropriation.

There was no claim of responsibility and no immediate indication of who was behind the attack on the crowd, which had gathered to demand the reinstatement of the commander, who survived.

A spokesman for the Jalalabad hospital confirmed eight people had been killed and 15 wounded.

The Taliban and Islamic State have frequently fought each other in Nangarhar and both have been targeted by sustained US air strikes.

In pictures: Isis' weapons factories Show all 11 1 /11 In pictures: Isis' weapons factories In pictures: Isis' weapons factories A mortar round fin manufactured by Isis in Gogjali, Mosul, November 2016 Conflict Armament Research In pictures: Isis' weapons factories Isis rocket components discovered in Gogjali, Mosul, Iraq in November 2016 Conflict Armament Research In pictures: Isis' weapons factories Isis mortars discovered near Karamlais, Iraq, in November 2016 CAR In pictures: Isis' weapons factories An Isis rocket launch frame in Qaraqosh, November 2016 Conflict Armament Research In pictures: Isis' weapons factories A memo from Isis' COSQC on quality control at a manufacturing facility in Gogjali, Mosul, November 2016 Conflict Armament Research In pictures: Isis' weapons factories Electrically-operated initiators manufactured by Isis in forces Gogjali, Mosul, November 2016 Conflict Armament Research In pictures: Isis' weapons factories Isis mortar tubes at a manufacturing facility in Karamlais, November 2016 Conflict Armament Research In pictures: Isis' weapons factories An Isis mortar production facility discovered in Gogjali, Mosul, in November 2016 Conflict Armament Research In pictures: Isis' weapons factories An Isis weapons manufacturing facilities near Mosul in November 2016 Conflict Armament Research In pictures: Isis' weapons factories Stocks of French-manufactured Sorbitol, Latvian potassium nitrate and Lebanese sugar at an Isis weapons factory in Iraq Conflict Armament Research In pictures: Isis' weapons factories A destroyed Isis weapons facility in Qaraqosh, Iraq, November 2016 Conflict Armament Research

But the exact nature of the relationship between the two groups is little understood. There have been isolated incidents in Afghanistan in which the fighters of both appear to have cooperated.

Afghan intelligence documents reviewed by Reuters this year showed security officials believe Islamic State is present in nine provinces, from Nangarhar and Kunar in the east to Jawzjan, Faryab and Badakhshan in the north and Ghor in the central west.

Isis has grown to become one of the country's most dangerous militant groups since it appeared around the start of 2015.