BEIRUT (AP) -- U.S.-backed Syrian forces made new progress against Islamic State militants along the southern bank of the Euphrates River on Saturday as the coalition positions itself to launch a decisive bid for Raqqa, the de-facto capital of the militants' so-called "caliphate."
The Kurdish-led Syrian democratic Forces said they were in control of 90 percent of the town of Mansoura, approximately 26 kilometers (16 miles) southwest of Raqqa.
The Britain-based Syrian Observatory for Human Rights said the SDF has been engaged in fierce fighting with IS militants along the southern bank of the Euphrates River, around Mansoura. The river leads to Raqqa.
Already, the forces have reached the northern and eastern gates of Raqqa, which lies on the northern bank of the river. On Wednesday, the Islamic State group's Aamaq news agency reported the coalition had destroyed Raqqa's main telecommunication's center.
The campaign has led to wide-scale displacement around the Raqqa province, according to the U.N, and conditions are deteriorating inside the provincial capital.
There are also reports of mounting civilian casualties, though they are difficult to confirm because of the war environment.
In May alone, nearly 95,000 residents fled their homes or shelters because of violence in the Raqqa province, according to the U.N.'s refugee agency, UNHCR. But others have returned to their homes as the SDF captures IS-held ground.
"The offensive on Raqqa has intensified over recent days, when more than 100 air and artillery strikes were reported to have caused many civilian casualties," the agency said in a June 1 report.
The violence around Mansoura has produced conflicting casualty allegations, common amid the fog of this war.
An airstrike leveled a school in the town on March 21, leading local monitoring groups to say at least 33 civilians taking shelter inside had been killed.
U.S. Lt. Gen. Stephen Townsend acknowledged days later that coalition aircraft bombed the school but said preliminary intelligence indicated the victims were IS militants occupying the building, not refugees.
Roadblocks and damage to bridges and infrastructure has driven up the prices of fuel and basic foodstuffs inside Raqqa, according to the U.N.'s humanitarian agency OCHA, compounding the hardship inside the extremist group's self-styled capital.
The U.S. has backed the SDF with weapons, airpower, and ground support in its campaign to defeat the Islamic State group in northern Syria. It began arming the fighters under a new order from the Trump administration in late May, to the dismay of Turkey, which says the factions receiving the weapons are terrorists affiliated with the Kurdish insurgency inside its own borders.
The SDF's target for now is Raqqa, which has been held by IS militants since 2014.