Four Russian servicemen have been killed by “militant fire” in Syria, Russia’s defense ministry said Sunday. 

Five other soldiers were wounded in the incident in Syria’s eastern Deir Ezzor province, according to the ministry, when “several mobile terrorist groups attacked a Syrian government artillery position at night.”   The ministry said the Russian casualties were “military advisors” to the Syrian troops

The statement did not say when the fighting occurred, although several reports suggested it may have taken place last Wednesday.

A monitor for the Syrian Observatory for Human Rights told the French News Agency nine Russian soldiers died Wednesday alongside at least 26 Syrian troops near Mayadeen town in Deir Ezzor.

The statement said 43 militants were killed in the resulting clashes.

The Russian statement raised the official count of Russian soldiers killed in Syria to 92.