IS attack kills dozens of regime forces near Palmyra

At least 20 Syrian regime forces were killed during clashes with the Islamic State group near Palmyra on Monday, a monitor said.

Two high-ranking officers were among those killed when IS militants shot down a government helicopter, the London based Syrian Observatory for Human Rights said.

"At least 20 regime forces and pro-government fighters were killed in an IS attack on Tayfur airport in Homs province. Two high-ranking Syrian officers were killed when a regime helicopter was shot down near the airport," the monitor said.

The head of the Britain-based monitor, Rami Abdel Rahman, said IS was using "successive attacks" to wear out regime forces, and that clashes were ongoing.

The militants retook Palmyra in central Syria on December 11, just eight months after the army backed by Russia drove them out, but the militants recently launched an offensive attempting to recapture the city.

On Thursday, US-led coalition aircraft destroyed heavy weaponry seized by the militants when they retook the city, the coalition said.

Among the weapons destroyed by US-led the anti-IS coalition were artillery, tanks and anti-aircraft systems, which the militants took from Russian and Syrian regime military bases in the Palmyra area.

"Coalition airstrike destroys a [IS] and artillery piece near Palmyra, Syria," the US-led Combined Joint Task Force said on its Facebook page, with a video showing the air strikes.

Palmyra is a UNESCO World Heritage site, and its recapture by IS gave the militant group a propaganda boost as they face assaults on two of their key strongholds - Raqqa in Syria and Iraq's second city Mosul.