Jalalabad, Afghanistan: Islamic State beheaded 15 of its own fighters due to infighting in Afghanistan's eastern province of Nangarhar, officials said, while a separate suicide attack on Thursday tore into a crowd in the provincial capital, Jalalabad, 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 Islamic State and the Taliban.

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

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

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

Nangarhar, on the porous border with Pakistan, has become a stronghold for Islamic State, generally known as Daesh in Afghanistan, which has grown to become one of the country's most dangerous militant groups since it appeared around the start of 2015.

Attaullah Khogyani, the provincial governor's spokesman, said the 15 Islamic State fighters were executed after a bout of infighting in the group, which has become notorious for its brutality. The killings occurred in the Surkh Ab bazaar of Achin district.

Further details were not available and there was no confirmation from Islamic State, whose local branch is known as Islamic State in Khorasan, an old name for the area that includes modern Afghanistan.

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

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.