Taking Yabroud, the last opposition bastion near the Lebanese border, could be a major victory for Syrian President Bashar al-Assad, whose image is seen in this file photo. (AP Photo/Muzaffar Salman)

Syrian government troops backed by Hezbollah fighters took full control of the strategic town of Yabroud on Sunday after driving out opposition forces, helping President Bashar al-Assad secure the land route connecting the capital city of Damascus with Aleppo and the Mediterranean coast.

The fall of Yabroud, the last opposition bastion near the Lebanese border, could sever a vital insurgent supply line and consolidate government control over a swathe of territory from Damascus to the central city of Homs.

The army "restored security and stability to Yabroud … after eliminating a large number of terrorist mercenaries," the Syrian military said in a statement hailing the strategic victory.

A military source said that about 1,000 fighters from the Al-Qaeda-linked Nusra Front had held out on Saturday to fight government forces, which had entered eastern districts of Yabroud and captured several hilltops.

"They fought a fierce battle and then from last night until the early hours of today they all pulled out," he said.

The source said the militants had withdrawn to the nearby villages of Hosh Arab, Fleita and Rankos as well as Arsal, a Lebanese border town 13 miles to the northwest.

Hezbollah-operated Al Manar television broadcast scenes from Yabroud's main square, where people walked around and talked in apparent safety. Soldiers replaced the three-star flag of the Syrian revolution with the government's two-star banner.

Footage from earlier in the day showed empty streets, shuttered shops and abandoned homes in a main thoroughfare. Heavy gunfire could be heard in the background.

The anti-Assad Syrian Observatory for Human Rights monitoring group said fighters from the Lebanese Shia Muslim group Hezbollah, who supported the Syrian army and pro-government fighters in sealing off the frontier area with Lebanon, were now in control of large parts of Yabroud.

The army had dismantled a large number of explosive devices planted by the rebels, Syrian state television said.

Thousands of civilians fled Yabroud, a town of about 40,000 to 50,000 people roughly 40 miles north of Damascus, and the surrounding areas after it was bombed and shelled last month ahead of the government offensive.

The government has been making incremental gains along the land route and around Damascus and Aleppo in the past months, regaining the initiative in the three-year uprising-turned-civil war which has killed more than 140,000 people.

The military source said that in parallel to the capture of Yabroud, the army and air force had closed 14 of 18 crossings into Lebanon, where violence has spilled over in the past year.

"In the next few days, the battle will be over closing these remaining crossings," the source said.

Syrian television said the army was targeting opposition fighters between Fleita and Arsal who had withdrawn from Yabroud. Al Manar said air raids had destroyed several trucks carrying fleeing opposition fighters near Arsal.

The military dropped barrel bombs on Ras al-Maara, an opposition-held village six miles east of the Lebanese border, killing at least six people including two children, according to the Observatory.

An influx of fighters into Lebanon from Syria threatens to further destabilize the small Mediterranean country whose own 15-year civil war ended in 1990. Sectarian tensions between Shia and Sunni Muslims there have already been heightened by the war in Syria, causing insecurity and political gridlock.

A local Lebanese official from Arsal told Al Arabiya television he wanted the Lebanese army to secure the border and prevent Sunni fighters fleeing Yabroud from entering his town.

"We in Arsal are not ready to accept militants. Even if we support the revolution, the militants' battle is in Syria, not in Lebanon. Arsal will not be the place from which war is sparked inside Lebanon," he said.

A Lebanese security source said that Lebanon's army was confronting insurgents crossing the border from Syria. Forces in Arsal detained a group of Syrians carrying "weapons of war and ammunition," Lebanon's National News Agency said.

In a separate incident, the army fired on opposition fighters in a pickup truck near Arsal after they bypassed a checkpoint, but failed to prevent their escape, the security source said.

A Nusra Front fighter in Yabroud denied that opposition fighters had planned to withdraw to Arsal.

Meanwhile, Saturday marked the third anniversary of the Syrian civil war. A day earlier, the United Nations refugee agency (UNHCR) said the country now leads the world in forced displacement, with more than 9 million people uprooted as a result of the conflict.

The total number of displaced people is comprised of over 2.5 million refugees who are living in neighboring countries and 6.5 million internally displaced persons (IDPs) within Syria, according to the UNHCR. The number of people uprooted — half of whom are children — equals 40 percent of the country’s pre-war population.

In crossing the 9 million mark, experts believe that Syria has overtaken Afghanistan as the country with the most forcibly displaced persons.

“It is unconscionable that a humanitarian catastrophe of this scale is unfolding before our eyes with no meaningful progress to stop the bloodshed," said U.N. High Commissioner for Refugees António Guterres. "No effort should be spared to forge peace. And no effort spared to ease the suffering of the innocent people caught up in the conflict and forced from their homes, communities, jobs and schools."

Al Jazeera and Reuters