Syrian men walk past destroyed buildings in the mountainous city of Zabadani, in the western countryside of Damascus, capital of Syria, on April 25, 2017. The towns of Madaya, Zabadani and nearby Buqain, Serghaya, Bludan, and Eastern Mountain, in the western countryside of Damascus, are now free of any rebel presence, with last busses evacuating rebels and their families left the towns on April 19. (Xinhua Photo)

DAMASCUS, April 30 (Xinhua) -- More than 200 rebels are believed to have been killed during a three-day infighting over control of territory east of the capital Damascus, a monitor group reported Sunday.

The infighting started on Friday, when the Jaish al-Islam, or Islam Army, unleashed a wide-scale offensive against the Front for Liberating the Levant, previously known as the al-Qaida-linked Nusra Front, in the Eastern Ghouta countryside of Damascus, said the Syrian Observatory for Human Rights.

The UK-based watchdog said the aim of the attack by the Saudi-backed Islam Army is to strip the Qatari-backed Nusra Front of areas in Ghouta.

The Observatory said at least five civilians were killed during the infighting.

Meanwhile, about 3,000 people protested on Sunday in Eastern Ghouta, demanding an end to the rebel-on-rebel battles, said the Observatory, adding that the Islam Army opened fire at the protestors to disperse them.

The Islam Army issued a statement later on Sunday, saying it "apologizes" for the shooting on civilians by its fighters during the protests, calling it a "wrong conduct."

The Eastern Ghouta, a sprawling, largely-agricultural land, has been long out of the government control and dominated by foreign-backed jihadi factions.

In recent months, the Syrian army and allied fighters succeeded to lay a kind of siege on that part of the capital, prompting the rebels to launch a surprise attack last month against the government-controlled east of Damascus, but they failed to make any breakthrough during two waves of attacks.

Observers believe that the infighting reflects the conflicting interests of regional backers, as each group wants to have the stronger foot on ground east of the capital.

The Nusra Front, or the Front for Liberating the Levant, has been branded by the UN and the international community as a terrorist group, and the U.S.-led anti-terror coalition has been targeting its leaders in Idlib Province in northwestern Syria.

The infighting in the Ghouta area plays into the hands of the government, whose troops fought intense battles when the rebels launched their major offensive from that part against the capital last month.