Islamic State in Iraq and Syria jihadist group executed eight men accused of being gay in central Syria on Monday, a monitoring group said.

The Syrian Observatory for Human Rights said the jihadists shot dead seven men in Rastan, a town in Homs province, "after accusing them of being homosexual."

ISIS also executed a man in the town of Hreitan, in the northern province of Aleppo, for the same reason, said Observatory head Rami Abdel Rahman.

He said the executions were carried out in public, but that ISIS fighters destroyed any cameras that had been used to film the killings.

ISIS has used brutal violence to enforce its rule in the so-called "caliphate" it declared across territory in Iraq and Syria.

Along with homosexuality, witchcraft and loyalty to President Bashar al-Assad are also considered capital punishment offences in ISIS-controlled areas.

In previous cases, ISIS has beheaded alleged homosexuals or thrown them from rooftops.

According to the Observatory, IS has executed more than 3,000 people since it announced its caliphate in June 2014.

The number includes at least 1,800 civilians.