Over 230 bodies of people believed to belong to the al-Sheitaat tribe have been found in a mass grave in eastern Syria after being killed by the Islamic State [IS], according to a monitoring group.

The grave was found in Syria's eastern province of Deir al-Zor, according to the Britain-based Syrian Observatory for Human Rights.

The monitoring group added that the deaths would bring the number killed by IS from the Sheitaat group to over 900.

Deir al-Zor is a city which has found itself at the heart of the Syrian civil war with major fighting between IS and other jihadist groups.

Earlier this month, the monitoring group reported that an IS suicide bomber detonated his device outside the Syrian military airport on the outskirts of the city.

The Syrian army has continued to fight IS in the city and the wider province, killing many militants, according to the Syrian state news agency, Sana.