Smoke rises from an emergency service point after an airstrike at the rebel-held village of Maar Zita in Idlib province, Syria April 27, 2017. (Xinhua/Reuters Photo)

DAMASCUS, May 28 (Xinhua) -- At least 20 civilians were killed when a U.S.-led airstrike struck their convoy near the northern city of Syria's Raqqa, state news agency reported on Sunday.

The warplanes of the U.S.-led anti-terror coalition targeted cars transporting civilians out of Raqqa between the towns of Ratleh and Kasrah on Saturday, said SANA.

The rate of civilian causalities by U.S.-led airstrikes has increased recently as a result of the intensification of U.S. airstrikes on Raqqa, the de facto capital of the Islamic State (IS) group, and other IS strongholds in northern and eastern Syria.

Last Thursday, 35 civilians were killed by U.S. strikes on IS-held city of Mayadeen in the eastern province of Deir al-Zour.

The Syrian government repeatedly denounced the attacks that target civilians, branding the operation of the U.S.-led anti-terror coalition in Syria as "illegitimate."

Last week, the Syrian Foreign Ministry said the U.S. targeting of civilians is part of a series of attacks carried out by the "illegal international coalition against Syria's sovereignty and territorial integrity under the pretext of combating terrorism, while the actions of this alliance only contribute to spreading chaos and destruction which benefits the extremist terrorist organizations, particularly IS and other terrorist organizations."

The ministry said that Syria condemns the U.S.-led attacks which target civilians and cause massive material damage to the infrastructure, facilities, and properties in Syria, calling on the UN Security Council to implement its resolutions on preserving the integrity of Syria's territory and people and stop the attacks of the illegal coalition.

It concluded by saying that Syria reiterates the importance of halting the illegal U.S.-led coalition's actions and implementing Security Council resolutions related to counter-terrorism, including resolution no. 2253.