At least 25 militants of Islamic State(IS) militant group were killed in powerful blasts at a weapon depot in eastern Syria killed on Wednesday, the Syrian Observatory for Human Rights reported.
Several explosions rattled the city of Mayadeen in the eastern countryside of Deir al-Zour province, Xinhua news agency reported.
It said 20 others were wounded and the toll could rise due to the large number of severely wounded militants.
The Britain-based watchdog group said that it was not clear what caused the explosion, whether it was a result of a bombing or a technical malfunction.
The IS group has captured large swathes of the oil-rich province of Deir al-Zour.