ISIS terrorist in Raqqa, Syria (file)
ISIS terrorist in Raqqa, Syria (file)Reuters

Warplanes from the American-led coalition on Friday pounded the Islamic State (ISIS) group with at least 150 strikes to bolster a major offensive on the jihadists' Syrian stronghold of Raqa, a monitor said.

The U.S. is backing twin assaults against ISIS -- one in Raqa province and another which aims to retake the Iraqi city of Fallujah across the border.

A Kurdish-Arab alliance is being supported by coalition air raids as well as Amer5ican forces on the ground in its push for territory north of Raqa city -- ISIS's de facto Syrian capital.

Turkey on Friday said it was "unacceptable" that U.S. troops had been seen near Raqa wearing insignia of Kurdish militia who belong to the U.S.-backed Syrian Democratic Forces (SDF) and who Ankara regards as a terror group.

The coalition has been providing air support to the SDF with 150 strikes on ISIS positions since the assault began Tuesday, according to the Syrian Observatory for Human Rights, a British-based monitor.

"There has been a serious intensification of air strikes," Observatory head Rami Abdel Rahman said.

SDF forces have pushed forward from Ain Issa, less than 60 kilometers (40miles) north of Raqa city, into the surrounding farmland and small villages.

The fighting and bombardment has left 31 ISIS fighters dead so far, Abdel Rahman said.

The number of SDF casualties was unclear.

The twin offensives come as world powers try to salvage a shaky ceasefire between the regime and non-jihadist rebels agreed in February to boost efforts to end a conflict that has killed more than 280,000 people.

The estimated 300,000 people still living in Raqa city are becoming increasingly desperate to flee.

According to anti-ISIS activist group Raqa is Being Slaughtered Silently (RBSS), residents were paying smugglers $400 (350 euros) each to try to escape.

"There is nearly no one walking in the streets," said RBSS activist Hamoud al-Musa.

"People are afraid of a brutal onslaught from the warplanes, whether coalition, Russian, or even regime," he told AFP.

ISIS had set up a few new checkpoints in Raqa city and was "amassing its forces on the front lines" further north, he said.

For the second time this week, coalition warplanes on Friday morning dropped leaflets encouraging residents to flee Raqa.

ISIS, which has tightened restrictions on movement, has been accused of using residents as human shields.

Abdel Rahman said a handful of families had fled the city to Idlib province, controlled by a rebel alliance including ISIS's jihadist rival, Al-Nusra Front.

AFP contributed to this report.

(Arutz Sheva’s North American desk is keeping you updated until the start of Shabbat in New York. The time posted automatically on all Arutz Sheva articles, however, is Israeli time.)