Russian warplanes have carried out dozens of air strikes on the Islamic State (IS) group's positions in the Syrian Desert, activists say.
The jets are supporting an operation by Syrian pro-government forces to secure the road between Homs and Deir al-Zour, according to a monitoring group.
IS militants have carried out a string of deadly ambushes and hit-and-run attacks in the region recently.
The latest, on Wednesday, reportedly killed nine soldiers and militiamen.
The UK-based Syrian Observatory for Human Rights, which monitors the war in Syria via a network of sources, said three others had died on Tuesday when a landmine planted by IS exploded in the desert near al-Mayadeen, in south-eastern Deir al-Zour province.
Russian air strikes on Tuesday killed at least 10 IS militants in Deir al-Zour and eastern Hama province, while there were no immediate reports of casualties from Wednesday's strikes in the al-Shawla area and what it described as "the Aleppo-Raqqa-Hama triangle", it added.
Syria TV, an opposition TV channel, also said that Russian jets were attacking IS positions in the desert Badiya region as part of an offensive by troops and militiamen.
However, Syrian state media made no mention of the reported operation.
IS once controlled 88,000 sq km (34,000 sq miles) of territory that stretched from western Syria to eastern Iraq and imposed its brutal rule on almost eight million people.
Despite the group's territorial defeats in Iraq in 2017 and Syria in 2019, UN experts estimate that more than 10,000 militants remain active in the region, pursuing protracted insurgencies. They are organised in small cells hiding in desert and rural areas, and are able to move across unprotected borders.
The UN's counter-terrorism chief, Vladimir Voronkov, warned last week "these sizable remnants are assessed to pose a major, long-term and global threat".
In a separate development on Wednesday, Turkish police said they had arrested two senior members of IS in Ankara and freed a seven-year-old girl from Iraq's Yazidi minority who was being held captive. One of the suspects was identified as a former Iraqi army officer.