DAMASCUS, June 18 (Xinhua) -- The U.S.-led coalition shot down a Syrian warplane carrying out a combat mission against the Islamic State (IS) group in Raqqa on Sunday, the Syrian army said in a statement.

Calling the action as a flagrant aggression, the general-command of the Syrian army said the downing of the Syrian war jet by the coalition is an evidence of the U.S. support for the terror groups.

The attack aims to undermine the capability of the Syrian army, "the only effective power practicing its legitimate rights in fighting terrorism across the homeland," said the statement.

"The attack comes at a time when the Syrian army is making strides in the war on IS terror group, which is collapsing in the Syrian desert thanks to the progress of the Syrian army and allied forces," it added.

The U.S.-led coalition shot down the Syrian warplane over the city of Rasafeh in the southern countryside of Raqqa, the de facto capital of IS.

It is the first time for the U.S.-led forces to have shot down a Syrian warplane during the Syria conflict.

The Syrian army warned of the "dangerous repercussions" of the attack, stressing that such acts will not dissuade the Syrian army from continuing its fight against the terrorist groups and restoring peace and security to all of Syria.

The incident comes as the Syrian army is advancing against IS in the southern and western countryside of Raqqa, while the U.S.-backed Syrian Democratic Forces (SDF) are fighting IS inside Raqqa.

It is not the first time for the United States to attack the Syrian government forces. The U.S. forces have struck Syrian military positions in the Syrian desert, where the Syrian army was advancing against IS.

In May, Russia, Turkey and Iran signed a memorandum of understanding on the establishment of four "de-escalation zones" in Syria's Idlib province, Homs province, Damascus outskirts and southern areas.

However, since mid-May, the U.S.-led coalition has entered the "de-escalation zones" multiple times to strike pro-government forces.

On June 9, state news agency SANA reported that the U.S.-led coalition carried out 25 airstrikes on the northern Syrian city of Raqqa over the past 24 hours, killing at least 17 civilians.

Russia has voiced strong opposition to U.S. strikes on pro-government forces in Syria. Russian Foreign Minister Sergey Lavrov earlier this month urged Washington to take measures to prevent such incidents from happening in the future.

Also on Sunday, Iran's Islamic Revolution Guards Corps (IRGC) announced that it has launched a missile attack targeting the terrorists command centers in Syria's Deir ez-Zor.

The missile attack aimed to punish the "Takfiri terrorists" for their recent twin attacks in Iran's capital Tehran, which claimed 17 lives and injured dozens of people, according to the IRGC's statement.

According to the reports, a large number of terrorists have been killed in the attacks and a large amount of weapons and ammunition have been destroyed, the statement said.

China has urged the Syrian factions, regional countries and the international community to be united in counter-terrorism efforts without adopting double standards.

China hopes that relevant parties in Syria will achieve reconciliation and eventually form a national reconciliation government, said Xie Xiaoyan, special envoy of the Chinese government on the Syrian issue.

At a news briefing in the Chinese embassy in Damascus on Saturday, Xie said China has been providing humanitarian assistance to Syria within its capacity.

The deal on de-escalation zones, which went into force in Syria last month and largely helped curb violence in some areas, is an important step towards resolving the Syria crisis, the Chinese envoy said.