DAMASCUS, Sept. 19 (Xinhua) -- The Islamic State (IS) militants unleashed a counter-offensive Wednesday against the U.S.-backed Syrian Democratic Forces (SDF) militia in eastern Syria, a war monitor reported.

The IS militants started its counter-offensive with the detonation of two booby-trapped vehicles targeting the Kurdish-led SDF positions in the Baghous area in the eastern countryside of Deir al-Zour province, said the Syrian Observatory for Human Rights.

The counter-attack comes against the backdrop of the wide-scale offensive that has been launched by the SDF, with the backing of the U.S.-led coalition, on the last IS-held pocket on the eastern bank of the Euphrates River in eastern Deir al-Zour on Sept. 10.

The IS militants are also attempting to thwart the advance of the SDF through planting mines, some of which are advanced and laser-controlled that are difficult to be detected.

The terror-designated militants also carried out suicide bombings to stop the SDF from advancing in the areas of Baghous and Hajin in the last IS-held pocket in the eastern countryside of Deir al-Zour.

Recent reports said the IS-controlled Syrian territory has shrunk to one percent from almost half of the country a couple of years ago.

The Syrian army has cleared the IS from large swathes of areas in Deir al-Zour Province, including its namesake capital city, while the SDF is attempting to consolidate positions in the northern and northeastern countryside of the province.