It is the latest attack of its kind by remnants of the jihadists.

They "attacked three military sites belonging to regime forces and fighters loyal to them... in the eastern Homs countryside, triggering armed clashes... and killing 15" pro-government fighters, the British-based Syrian Observatory for Human Rights said.

IS overran large swathes of Syria and Iraq in 2014, proclaiming a so-called caliphate and launching a reign of terror.

It was defeated territorially in Syria in 2019, but its remnants continue to carry out deadly attacks, particularly against pro-government forces and Kurdish-led fighters in the vast desert.

IS remnants are also active in neighbouring Iraq.

Last month, IS group fighters killed 28 Syrian soldiers and affiliated pro-government forces in two attacks on government-held areas of Syria, the Observatory said.

Many were members of the Quds Brigade, a group comprising Palestinian fighters that has received support from Damascus ally Moscow in recent years, according to the Observatory, which has a network of sources inside Syria.

In one of those attacks, the jihadists fired on a military bus in eastern Homs province, the Observatory said at the time.

Separately, six Syrian soldiers died in an IS attack against a base in eastern Syria, it added.

Syria's war has claimed the lives of more than half a million people and displaced millions more since it erupted in March 2011 with Damascus's brutal repression of anti-government protests.

It then pulled in foreign powers, militias and jihadists.

In late March, IS militants "executed" eight Syrian soldiers after an ambush, the monitor said at that time.

The jihadists also target people hunting desert truffles, a delicacy which can fetch high prices in the war-battered economy.

The Observatory in March said IS had killed at least 11 truffle hunters by detonating a bomb as their car passed in the desert of Raqa province in northern Syria.

In separate unrest in the country, Syria's defence ministry earlier on Friday said eight soldiers had been injured in Israeli air strikes near Damascus.

The Observatory said Israel had struck a government building in the Damascus countryside that has been used by Lebanon's Iran-backed Hezbollah group since 2014.

The Israeli military has carried out hundreds of strikes in Syria since the outbreak of Syria's civil war, mainly targeting army positions and Iran-backed fighters.