BEIRUT - The Islamic State group stoned two men to death in Syria Tuesday after claiming they were gay, a monitor said, in the jihadist organisation's first executions for alleged homosexuality.

‘The IS today stoned to death a man that it said was gay,’ the Syrian Observatory for Human Rights said, adding that the victim was around 20 years old. He was killed in Mayadeen in the eastern province of Deir Ezzor, near the border with Iraq.

The Britain-based Observatory said IS claimed it found videos on his mobile phone showing him ‘practising indecent acts with males’. In a separate incident on Tuesday, an 18-year-old was also stoned to death in Deir Ezzor city after the group said he was gay, the Observatory said. Activists on social media said that the dead men were opponents of IS and that the group had used the allegation as a pretext to kill them.

The United Nations said this month the IS had carried out several executions by stoning of women in Syria it accused of adultery. The jihadists proclaimed a ‘caliphate’ in June after seizing swathes of Iraq and Syria. Activists say IS carries out regular public executions - often beheadings - in areas it controls. Moreover, A string of Syrian regime air strikes on the Islamic State group's self-proclaimed capital Raqa on Tuesday killed at least 63 people, more than half of them civilians, a monitor said.

The air strikes were the deadliest by President Bashar al-Assad's air force against Raqa since the Sunni extremist IS seized control of the city last year. ‘Among the 63 killed were at least 36 civilians,’ said Rami Abdel Rahman of the Syrian Observatory for Human Rights.

‘There were also 20 unidentified victims who could be civilians or jihadists, as well as the disfigured remains of at least seven other people,’ he said.

The director of the Britain-based monitoring group said previously that ‘most of the casualties were caused by two consecutive air strikes’ on Raqa's main industrial zone.

‘The first strike came, residents rushed to rescue the wounded, and then the second raid took place,’ Abdel Rahman, whose group relies on a network of sources on the ground in Syria for its information, told AFP. Amateur video footage distributed by activists in Raqa showed several bloodied bodies laid out on a street near an apparent bombing site, as an ambulance rushed to the scene.

Aid workers in red overalls bearing the Red Crescent symbol could be seen placing the corpses into white body bags. Activists from the city meanwhile denounced the raids as a ‘massacre’. The Islamic State organisation emerged in Syria's war in spring 2013. It took over Raqa, the only provincial capital to fall from government control since the outbreak of a 2011 revolt, and turned it into its bastion.