Turkey eyes Raqqa as noose tightens around Islamic State in al-Bab

Syrian rebel forces supported by the Turkish army seized strategic hills around the Islamic State-controlled al-Bab overnight and pushed into western areas of the Syrian town, reports said on Wednesday.

The Turkish military said in a written statement that 58 Islamic State militants were killed in air strikes, artillery fire and clashes as part of those operations.

Four soldiers were killed and 15 wounded on the Turkish side, the Turkish military said.

Turkish Prime Minister Binali Yildirim said their forces had taken control of the outer districts.

"Currently the town is besieged from every side. The outer districts of the town have been brought under control," Yildirim told a news conference in Ankara broadcast live.

Videos were posted on Twitter of Turkish-backed forces fighting and travelling towards the town.

A rebel offical meanwhile reported that the Turkish army and allied Syrian rebels had taken the western outskirts of the town.

"With last night's assault, Islamic State's defences have been broken through and the advance is now continuing," a Turkmen Syrian rebel official told the Reuters news agency from the Turkish city of Gaziantep.

Turkey's foreign minister, Mevlut Cavusoglu, said on Wednesday the next target after al-Bab would be Raqqa, the last major town under the control of IS in Syria.

"We should and can insert special forces into Raqqa," he told Haberturk TV. "Unfortunately the previous US administration didn't co-operate with us - but we hope to work better with this one."

US-backed forces from the Kurdish-led Syrian Democratic Forces have already started operations to take Raqqa. Turkey views the SDF's Kurdish contingent, the YPG, to be a terrorist organisation and has clashed with its members in northern Syria.

In a video sent by the rebel official, three Syrian rebel fighters with the Sultan Murad faction said they were speaking from inside al-Bab. It was not possible to confirm the authenticity of the footage.

"I am in al-Bab now but not at the centre. We are on the outskirts. Thank God, we have reached this place," said one of the rebels. Blasts were heard in the background.

Other videos showed troops travelling in convoy.

Syrian government forces have also advanced to within a few kilometres of al-Bab, which is located 40km northeast of Aleppo.

The separate campaign by the Syrian army has raised the risk of a clash with the Turkish military.

The Syrian Observatory for Human Rights, a UK-based organisation that reports on the war, also reported the hill had been taken.

"We don't know if Daesh (Islamic State) will be able to recover, or if it is in a state of collapse," said the Observatory director, Rami Abdulrahman.

Ibrahim Kalin, spokesperson for the Turkish presidency told private broadcaster NTV that Turkey has tabled a concrete plan on Raqqa and the matter will be discussed during the CIA director’s expected visit to Turkey on Thursday.

He said US President Donald Trump had reacted positively to the plan. He also said the groundwork was being laid for a joint offensive on Raqqa.