At least 28 Syrian government soldiers and pro-regime fighters were killed Wednesday (July 19th) in a rebel ambush in the Eastern Ghouta region near Damascus, AFP reported.

The fighters came under attack by the Army of Islam opposition group as they attempted to advance in the town of al-Rihan, the Syrian Observatory for Human Rights said.

The Eastern Ghouta region is a major opposition stronghold near the capital, and it has been the frequent target of government military operations.

Observatory director Rami Abdel Rahman said opposition fighters opened fire on the government troops as they entered an area where the fighters had planted mines.

The ambush was the deadliest incident for government fighters in Eastern Ghouta since February 2016, when 76 regime troops were killed in Tal Sawane, he said.

Eastern Ghouta is in one of the four proposed "de-escalation zones" designated in an agreement reached by government allies Iran and Russia and opposition backer Turkey in May.

But the deal has yet to be fully implemented over disagreements on the monitoring mechanism for the safe zones.