Syrian opposition fighters will be allowed to leave the last rebel-held neighbourhood in the city of Homs under a Russia-backed deal signed on Monday.

According to Talal Barrazi - governor of Homs province, where Homs city is the capital - the deal is to be carried out within six to eight weeks.

It follows other agreements that were never fully implemented between the government and rebel groups in al-Waer, their last bastion in Homs, which has been pounded by air strikes in recent weeks.

Homs, the country's third-largest city, was once the centre of the uprising against President Bashar al-Assad.

Throughout Syria's war, now at the end of its sixth year, wide parts of the city were held by rebels but state forces eventually regained control of all areas except for al-Waer.

Al-Waer is home to about 75,000 people and has been under a government siege since 2013, triggering shortages of medicine and occasionally food.

The UN has not been able to deliver much-needed humanitarian aid to the area since September 2016.

Barrazi's statement, carried by state SANA news agency, said the evacuation is the third phase of a deal reached last year that saw hundreds of fighters and their families leave al-Waer for other rebel-held areas.

Opposition activist Bebars al-Talawy said the agreement was signed on Monday, adding that a committee will be formed to prepare the lists of names of those who want to leave.

"People are happy that they will get rid of the siege, but sad because they will leave Homs," Talawy said.

The UK-based Syrian Observatory for Human Rights said 12,000 al-Waer residents will be displaced, including 2,500 fighters. It said the first 1,500 people will be evacuated next week.

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Those who leave will be taken to rebel-held areas in the countryside of Homs, the northwestern province of Idlib, and the town of Tal Abyad near the border with Turkey, according to the Syrian Observatory.

Monday's deal followed weeks of intense bombardment and air strikes on the neighbourhood that left 250 killed or wounded.

Syria's war pits Assad's forces, backed by Russia and Iran, against rebels supported by the United States, Turkey, and Gulf kingdoms, along with hardline groups affiliated with al-Qaeda.

Assad's government has increasingly tried to press besieged rebel areas to surrender and accept what it calls "reconciliation agreements", which involve fighters departing for northern Syria with small arms.

Moscow, Ankara and Tehran are pressing ahead with a fresh round of Russian-led Syria talks in Kazakhstan, despite a request from Syrian rebels to delay the meeting over ceasefire violations.

A Syrian government delegation arrived in the Kazakh capital Astana late on Monday evening.

The Astana talks, now in their third round, began in January in efforts to shore up a widely violated ceasefire between the sides that was brokered in December by Russia and Turkey.

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Syria's future will be decided only after "getting rid of extremists" and achieving political reconciliation, the country's President Bashar al-Assad said in an interview published on Monday.

As the war that has ravaged his country approaches its seventh year, Assad told reporters it was "still early to talk about" his vision for Syria's future.

"It's a luxury now to talk about politics while you're going to be killed maybe in a few minutes, you have terrorist attacks," he told a group of Western journalists, state news agency SANA said.

"So this is the priority, getting rid of the extremists, the political reconciliation in the different areas, this is another priority."

On Wednesday, Syrians mark the sixth anniversary since the beginning of the conflict, which the Syrian Observatory says has killed some 465,000 people, including 96,073 civilians.