DAMASCUS, Feb. 11 (Xinhua) -- The Islamic State (IS) group on Monday launched a counter-offensive against the U.S.-led forces in eastern Syria with suicide bombers, a war monitor reported.

The IS militants unleashed their counter-attack with three suicide bombers, targeting the Kurdish-led Syrian Democratic Forces (SDF) and the U.S.-led coalition in the eastern Euphrates River region, said the Syrian Observatory for Human Rights.

The IS militants are trying to protect the last three sq km they control in the eastern Euphrates region against the attacks of the U.S.-backed SDF, according to the UK-based watchdog group.

This comes amid ongoing clashes between the SDF and the IS coupled with shelling and airstrikes by the U.S.-led coalition against the IS positions.

A total of 13 IS militants and six SDF fighters have been killed during the counter-offensive.

On Saturday, the U.S.-backed SDF started on the final stage of attacks against the IS in the eastern Euphrates River region in eastern Syria.

Following the evacuation of over 20,000 civilians from the town of Baghouz in the eastern countryside of Deir al-Zour, the SDF started on Saturday night the operation against the remaining IS-held pocket in the eastern Euphrates region, according to Mustafa Balli, the head of the SDF media office.

Balli said that the battle aims to eliminate the last IS militants in the town of Baghouz.

After losing the four sq km, the IS will still control 4,000 sq km in the Syrian desert in eastern Syria.

The U.S.-backed SDF have been on a crushing offensive to root out IS from the eastern Euphrates region since last September.

The SDF managed, with the help of the U.S., to defeat IS in much of the areas it had controlled in the eastern Euphrates area.

The Syrian Observatory for Human Rights said over 37,000 civilians, including tens of IS militants, have fled the last IS-held pocket to areas controlled by the SDF in the eastern Euphrates area since last December.