At least 38 Islamic State (ISIS) group fighters were killed in United States-led coalition air strikes this week near Syria's ancient city of Palmyra, a monitor said on Saturday, according to AFP.

The jihadists retook Palmyra in central Syria on December 11, just eight months after the army backed by Russia drove them out.

On Thursday, U.S.-led coalition aircraft destroyed heavy weaponry seized by the jihadists when they retook the city, the coalition said.

A statement on Friday said the strikes destroyed an air defense artillery system, 14 tanks, three artillery systems, two ISIS-held buildings and two tactical vehicles.

Among the Russian weaponry ISIS captured around Palmyra were thought to be modern surface-to-air missiles, or SAMs, giving jihadists the potential capability to shoot down aircraft, a coalition official told AFP.

The Syrian Observatory for Human Rights, a monitoring group based in Britain, said that "at least 38 ISIS members were killed in the air strikes".

The strikes, near the Tiyas military air base northeast of Palmyra, helped regime forces gain some ground west of the fabled city, said the Observatory.

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

ISIS overran Palmyra, known as the "Pearl of the Desert", in May of 2015 and proceeded to blow up UNESCO-listed temples and looted relics that dated back thousands of years.

The jihadist group used Palmyra's grand amphitheater for a massacre in which child members of the group killed 25 Syrian soldiers, execution-style, in front of residents.

It also beheaded Palmyra's 82-year-old former antiquities director last August.

AFP contributed to this report.