More than 170 Islamist rebel fighters, including Saudis, Qataris and Chechens, were killed Wednesday in a Syrian army ambush near Damascus, AFP reported, citing the state news agency SANA.

The attack, apparently the deadliest against the rebels for months, took place in Eastern Ghouta, a key rebel stronghold targeted in a chemical attack in August 2013 that killed hundreds of people.

SANA said an army unit “spotted Al-Nusra Front (jihadist) and Liwa al-Islam (Islamist) terrorists” near Damascus, and “killed 175 of them and wounded several others.”

Saudis, Qataris and Chechens were among the dead, it said.

State television had earlier reported “dozens” killed, mostly non-Syrians, in a “well-organized ambush” following a tip-off.

The army also seized the rebels’ weapons, the broadcaster said, following the regime’s practice of using the term “terrorists” to refer to the armed opposition.

The Syrian Observatory for Human Rights, a Britain-based group with a network of contacts inside Syria, confirmed to AFP that dozens were killed in the ambush.

“Dozens of Islamist fighters were killed and wounded in an ambush by loyalist troops, with the help of Hezbollah, near Otaybeh village in the Eastern Ghouta area,” it said.

A government security source said most of the fighters were Jordanians or Saudis, and that they had crossed over into Syria from Jordan earlier the same day.

The source said the ambush took place at around 5:00 a.m. and killed 156 rebels. Another 10 were taken prisoner, said the source, speaking on condition of anonymity.

Wednesday’s ambush, seen as a success for Assad’s troops, came a day after the inter-rebel war in Syria heated up, as the leader of the Al-Qaeda-affiliated Al-Nusra Front gave rival jihadists an ultimatum to accept arbitration by clerics or be expelled.

Abu Mohammed al-Golani warned the rival Islamic State of Iraq and the Levant (ISIS) that it would be driven from Syria and “even from Iraq” if it did not comply within five days.

The threat came after Sunday’s killing of  an Al-Qaeda emissary, Abu Khaled al-Suri, at the hands of ISIS rebels.

The civil war in Syria has attracted many jihadist rebel groups which have been fighting the more moderate rebel groups in what has turned into a second war.

In recent weeks, the infighting between rebels has worsened, as three powerful rebel alliances – among them Islamist groups – have teamed up to fight ISIS, which they have warned is even worse than Assad’s regime.