Syria's army and its allies have broken a three-year rebel siege of two Shia towns in northwest Syria, the government and rebel groups said, cutting off a main supply route to nearby Turkey.

The breakthrough comes after days of rapid military gains north of the major city of Aleppo, with Russian air strikes playing a key role in the advance.

The two towns of Nubul and Zahraa, with an estimated 60,000 population, are connected to the border by areas under the control of Kurdish militias that provided access.

The Levant Front rebel group said the siege was broken "after three days of legendary resistance by the revolutionaries facing the Russian military machine, and after more than 500 raids by Russian air planes", Reuters news agency reported.

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Syria's state news agency SANA reported on Thursday "mass celebrations in the streets of Nubul and Zahraa welcoming army troops and celebrating the breaking of the siege".

The Al-Manar television station of Lebanese militia Hezbollah broadcast what it said was exclusive footage of Syrian government and allied fighters entering the towns. The channel showed crowds embracing soldiers and militiamen who fired into the air as they arrived.

The two towns had been besieged by rebels since 2012, and reaching them had long been a goal of the government, which has also sought to sever key rebel supply routes into Aleppo from Turkey.

Al Jazeera's Zeina Khodr, reporting from Gaziantep, Turkey, said that in taking the towns, the government achieved in three days what it's been trying to do for three years.

"There is no doubt this is a decisive turning point because at the end of the day, Turkey is the lifeline for the opposition. What we understand from pro-government sources is that this is just the beginning - the aim is to reach the Turkish border."



Meanwhile, UN-mediated talks in Geneva to end the war in Syria were paused on Wednesday until February 25.

US Secretary of State John Kerry blamed the Syrian government and its Russian allies for the stall in negotiations.

"The continued assault by Syrian regime forces - enabled by Russian air strikes - against opposition-held areas, as well as regime and allied militias' continued besiegement of hundreds of thousands of civilians, have clearly signalled the intention to seek a military solution rather than enable a political one," Kerry said in a statement.

Sergei Lavrov, the Russian foreign minister, said on Wednesday that the bombardment would continue. "Russian strikes will not cease until we really defeat terrorist organisations like Jabhat al-Nusra. And I don't see why these air strikes should be stopped," he said.

The conflict, that has lasted nearly five years, has resulted in more than 250,000 Syrians being killed. The civil war has also displaced millions more and sent hundreds of thousands fleeing as refugees to Europe.

Steven Heydemann, a professor of Middle East studies at Smith College in the US, told Al Jazeera that the country was now likely to see an upsurge in fighting after the military advancements by government forces.

"My sense is that what we have now created are incentives for the opposition and its regional backers to escalate their military activity in response to what they're confronting from the regime and that we're entering a period where we'll see a spiral upward in the level of violence," Heydemann said.



The Syrian government and its allies were also on the offensive against rebels south of Aleppo, Syria's commercial centre, and against Islamic State of Iraq and the Levant to the east of the city split between government and rebel control.

Alongside heavy Russian aerial support, the advances have been made possible by ground troops from Lebanon's Hezbollah movement and Iranian-backed militias that support President Bashar al-Assad's government.

The Russia air strikes that began in September tilted the war in Assad's favour.

Reports said pro-government militias from the besieged towns were able to link up with advancing Syrian army troops after the town of Maarsteh al-Khan fell.

Breaking the siege opens a direct route for the Syrian army to Kurdish-controlled Afrin and brings them closer to areas run by Turkish-backed rebels near the Turkish border.

Defence strategists said that the two heavily garrisoned towns could become a launching pad for the Syrian army and its allies for wider territorial gains in northern Aleppo province and to tighten the encirclement of the rebel-held part of Aleppo city.