US-led coalition air strikes destroyed early Friday two key bridges used by the Islamic State group on the Syrian side of the Iraqi border, a monitoring group said.

The Pentagon confirmed strikes in the area, and a senior US officer said they will have a "profound impact" on IS abilities to carry out operations in the neighbouring and strategically important Iraqi province of Anbar.

The coalition "destroyed two bridges between the Syrian city of Albu Kamal and the Iraqi border," said Rami Abdel Rahman, director of the Syrian Observatory for Human Rights.

"These bridges are strategically important for IS's movements between Albu Kamal and Iraq," he said.

The jihadists seized Albu Kamal and the nearby border crossing in July 2014, linking their territory in the eastern Syrian province of Deir Ezzor to areas they control in Iraq's western Anbar province.

The two bridges leading out of Albu Kamal -- one to the east, and one to the southeast -- were IS's "main routes to the Iraqi border," Abdel Rahman said.

The bridge running to the east crosses the Euphrates River and leads to Baghouz, a smaller town along the border.

To the southeast of Albu Kamal, a road crosses the bridge runs over a smaller river and continues as a road leading directly to the border.

"Using these bridges, it would take IS only a few minutes to reach the Iraqi border from Albu Kamal," Abdel Rahman said.

"The strikes do not cut off IS's route to Iraq, but they make IS movements there more difficult, because it will take them longer and they will be in view (of the coalition) for a longer period of time," he added.

The Pentagon confirmed the air raids, saying they had struck IS-held bridges in Deir Ezzor province.

"Coalition forces struck multiple Daesh (IS) targets in the vicinity of the eastern Syria border to reduce the freedom of movement of Daesh," said Brigadier General Kevin Killea, chief of staff of the US-led coalition.

"These strikes will have a profound impact on the ability of Daesh in Syria to affect operations in Iraq, particularly in Ramadi," capital of Anbar province, Killea said.

The coalition began its air campaign on IS positions in Syria last September, after the jihadists' spectacular advances on both sides of the border.