The Syrian Democratic Forces (SDF) were tightening the noose on Sunday (October 1st) around "Islamic State of Iraq and Syria" (ISIS) elements holed up in al-Raqa's national hospital, one of the last ISIS-held positions in the city, AFP reported.

The Arab-Kurd alliance has ousted ISIS from around 90% of the northern city but the group's elements still hold a pocket of central al-Raqa.

Less than 150 metres west of the hospital on Sunday, SDF fighters manned positions on the fourth floor of a heavily damaged building overlooking the hospital and the no-man's land below.

Periodically, they fired heavy machine guns at the massive complex then monitored carefully to identify the source of the returning fire.

"We are at the end of al-Raqa," said Amjad Siryani, a local commander with the SDF's Syriac Military Council.

There are two positions left: the stadium and the few surrounding buildings, and the national hospital, he said.

Siryani, 28, said his position was around 120 metres from the hospital where ISIS snipers, too, were watching.

"One of our comrades was hit by a sniper in his leg. We were able to identify where the shot came from and shoot him down," he said.

SDF fighters and ISIS exchanged rocket and mortar fire throughout the day on Sunday, and several airstrikes by coalition warplanes could be heard across the city.

The Kurdish and Arab fighters are positioned around the hospital in several multiple-storey buildings, many of them hollowed-out concrete carcasses of apartment complexes.

Children used as shields

The SDF's goal, its fighters said, was to isolate the ISIS-held hospital from the stadium to the north-west, but they have yet to break into either position.

"The reason we have not stormed the hospital yet is because there are civilians there," said Siryani, who said he had seen ISIS elements use children as human shields near the complex.

In a nearby position, SDF fighter Mohammad Selmo said he was often tasked with monitoring the hospital overnight and had heard crying children from inside.

"We are observing and waiting for the order to storm the hospital. If we see anyone coming out of it, they die," the young fighter told AFP.

"Once we take the hospital, it is over. It is important because there are a lot of ISIS fighters there."

The international coalition has said that it and the SDF are aware of reports that civilians inside are being used as human shields.