BEIRUT (Reuters) - The Syrian military has mounted air strikes against Islamic State militants and clashed with the jihadists in central Syria, the pro-Damascus al-Watan newspaper reported on Tuesday.

The flare-up in the area of al-Sukhna, between Palymra and Deir al-Zor, on Monday points to the foothold the ultra-hardline Islamist group still has west of the Euphrates even as U.S.-backed fighters are poised to seize its last enclave east of the river.

The Syrian air force mounted “a number of air strikes targeting Daesh movements in the eastern Badiya, specifically on one of the dirt roads leading to the town of al-Sukhna and southeast of the town”, al-Watan said, citing a military source.

Daesh is the Arabic acronym for Islamic State.

The U.S.-backed Syrian Democratic Forces (SDF) have been laying siege to Islamic State’s last enclave east of the Euphrates, the village of Baghouz, for several weeks.

Some 200 of the jihadists surrendered in Baghouz after a ferocious battle at the weekend, but around 1,000 may still be holding out, a spokesman for the U.S.-backed Syrian force battling them said on Monday.

In Washington, Pentagon spokesman Commander Sean Robertson said that in addition to the nearly 1,000 foreign fighters held by the SDF, there were thousands of other suspected Islamic State militants from Iraq and Syria held by the U.S.-backed group.

While the group’s defeat at Baghouz would mark a milestone in the fight against Islamic State, the group is expected to remain an insurgent threat inside Syria and Iraq.

The Syrian army recaptured Sukhna from Islamic State in 2017 as it pushed the jihadists back across central Syria in an advance along the crucial desert highway from Palmyra to Deir al-Zor.

However, some of its fighters remained in the rugged desert areas around and have carried out attacks on army positions and convoys, a pro-Damascus source has said.