At least 18 Syrian soldiers were killed and 20 wounded on Thursday when an explosive device detonated on a military bus in the Damascus countryside, local outlet Sham FM said.

Nobody claimed responsibility for Thursday's attack and there has been no comment from Syrian authorities.

The Syrian Observatory for Human Rights, a war monitor that counts casualties and covers military developments in the 11-year conflict, had earlier in the day said that 17 soldiers were killed in the blast.