The Islamic State group is "completely besieged" in its last major stronghold in Syria's Aleppo province, a monitor said Monday, as pro-regime forces piled pressure on the militant s on several fronts.
IS fighters were cut off in Al-Bab after forces loyal to the government of President Bashar al-Assad severed a road into the northern town, the Syrian Observatory for Human Rights reported.
"Al-Bab is now completely besieged by the regime from the south, and the Turkish forces and rebels from the east, north and west," said the Britain-based monitor.
It came after "the regime's forces and allied militia seized the only and last main road used by the militant s between Al-Bab and Raqa," Observatory chief Rami Abdel Rahman told AFP, referring to the militants' de facto capital in Syria.
Regime forces were backed by fighters from Lebanese Shia movement Hezbollah and by Russian artillery, said the Observatory, which relies on a network of sources on the ground for its reports.
The town of Al-Bab, 25 kilometres (15 miles) south of the border with Turkey, is seen as a prize by nearly all sides in the complex war.
Since December, Turkey-backed rebel fighters known as the Euphrates Shield alliance have edged towards Al-Bab from the north.
"Al-Bab is more important for the Turks, who defined the town as a priority for their Euphrates Shield alliance," said Syria expert Thomas Pierret.
But the regime, Pierret said, was eyeing territory around Al-Bab "to protect the eastern flank of Aleppo city," which it recaptured from rebels in December.
It also sought to use the town as a buffer, "preventing the Euphrates Shield from advancing south" deeper into Syria, he added.
Turkey and Russia back opposing sides in the war, but have joined forces in recent months to try to end to the conflict.
The two powers carried out their first joint bombing raids around Al-Bab in January after brokering a fragile ceasefire agreement between rebels and regime forces.
Along with Iran, they organised a summit in Kazakhstan in a bid to reinforce that truce ahead of full-fledged peace talks in Geneva later this month.
Those negotiations, hosted by UN special envoy for Syria Staffan de Mistura, are the latest attempt to stop the six-year conflict raging in Syria.
Several rounds of indirect talks in 2016 between the regime and the opposition, represented by the High Negotiations Committee, fizzled out without notable progress.
The HNC will announce on January 12 the members of its delegation to this month's talks, the leading Istanbul-based National Coalition said Monday.
The main obstacle to progress in previous rounds has been the fate of Assad, who opposition forces say must leave power at the beginning of any transition period.
On Monday, the Syrian president told visiting Belgian parliamentarians that Western policies towards the conflict raging in his country had actually hurt Europeans.
"Most European countries adopted an unrealistic policy since the beginning of the war in Syria... damaging the interests of their own people by supporting terrorist groups," Assad said.
Assad's regime has refocused on IS since fully recapturing Aleppo city in December, in the biggest blow to rebel forces fighting to topple his regime for nearly six years.
IS is among several militant movements that have shot to prominence during the conflict, which has left more than 310,000 people dead and has forced millions more from their homes.
Assad's forces were also locked in fighting with IS in the central province of Homs at the weekend, the Observatory said.
It reported that the troops had captured the Hayyan oilfield west of the celebrated desert city of Palmyra.
They also fought back against IS around Al-Seen military airport northeast of Damascus, said the monitoring group.
IS is facing simultaneous offensives in Syria and Iraq against its self-proclaimed Islamic "caliphate".
On Saturday, US-backed Kurdish and Arab fighters announced a new phase in their campaign to capture Raqa, but said they needed more weapons to win.
The Syrian Democratic Forces launched their offensive for the key militant stronghold in November and have taken some ground further up the Euphrates Valley but are still some distance away.
SDF fighters have received training and air support from the US-led coalition against IS. Last week Washington said it had provided them with armoured sports utility vehicles for the first time.
US President Donald Trump, who made fighting "radical Islamic terrorism" a central plank of his election campaign, was due to visit US Central Command on Monday, meeting officers who will spearhead his new strategy to defeat IS.
In late January, Trump ordered generals to begin a 30-day review of the US strategy to defeat the militant group.