DAMASCUS: Syrian troops advanced Saturday on the key rebel bastion of Yabroud as the country's civil war entered its fourth year, with more than 146,000 dead, millions displaced and peace efforts stalled.
Army troops were locked in fierce clashes with rebel forces, including the Al-Qaeda affiliate Al-Nusra Front, after they entered the town on Friday.
The strategic stronghold is the last rebel-held town in the Qalamun region, which lies along the border with Lebanon and on the key highway between Damascus and third city Homs.
The latest fighting illustrated the intractability of the conflict that began on March 15, 2011 after popular uprisings that toppled dictators in Tunisia and Egypt.
Protests erupted in Syria's southern city of Daraa after teenagers were arrested over graffiti declaring: "The people want the fall of the regime."
President Bashar al-Assad's regime reacted with force, and people began to die in the demonstrations that grew week after week.
Civilians took up arms, soldiers began to desert and an insurgency became full-scale civil war after the regime bombed the central city of Homs in February 2012.
Two years later, the war appears to have reached stalemate, with some predicting it could last another 10 or 15 years, like the 1975-1990 civil war in Lebanon.
Rebels control large swathes of the country, but are fighting both the regime and an Al-Qaeda-inspired group they once welcomed.
And the government holds the more densely-populated regions, seeking to protect "useful Syria" -- the coast, major towns and key roads.
The regime is advancing on three fronts, south of Damascus, in the strategic Qalamun region and in Aleppo in the north.
- Assad's army advancing -
In Aleppo, once Syria's commercial capital, the regime has retained the city's west, while advancing around the outskirts of the rebel-held east and securing and reopening the nearby airport.
Syria's mostly exiled political opposition has secured Western recognition but is largely ignored by rebels on the ground.
And it failed to achieve any progress in long-mooted talks with the regime in Geneva earlier this year, with the opposition demanding Assad step down and the regime ruling out that possibility.
Instead, Assad is already gearing up for elections in mid-2014 that he is expected to win.
On the ground, both sides have been accused of carrying out abuses, with the regime jailing and torturing thousands and dropping so-called barrel bombs that rights groups say fail to discriminate between fighters and civilians.
Rebels too are accused of summary executions and other violations, particularly the jihadist Islamic State of Iraq and the Levant.
- Nine million have fled -
The human cost of the conflict has soared, with nine million people forced from their homes, creating the world's largest displaced population, according to the UN's refugee agency.
More than 2.5 million Syrians are registered or awaiting registration as refugees in neighbouring countries, and in excess of 6.5 million people are displaced inside the country.
The total number who have fled their homes now exceeds 40 percent of the pre-conflict population, the UN said.
The exodus has strained the neighbouring countries disproportionately bearing the burden of the new arrivals, including small Lebanon, which is housing nearly one million Syrians.
UN refugee chief Antonio Guterres on Saturday urged all nations to open their doors to Syria's refugees.
"To see Syrian children drowning in the Mediterranean today after fleeing the conflict... is something totally unacceptable," he said.
"Borders need to be open everywhere, visa policies need to be open everywhere, family unification programmes need to exist everywhere."
Aid groups are urging government and citizens to continue to donate to relief efforts with no end to the humanitarian disaster in sight.
A generation risks being "lost forever" with millions of Syrian children deprived them of health care, education and security, they warned Saturday.
Experts say neither side can score a decisive military victory and the country is gradually splintering.
"Rebel infighting has helped Assad take back some areas, but the advances are not dramatic enough to tip the balance and allow him to reclaim the rest of Syria," Aron Lund, editor of the Carnegie Endowment's Syria in Crisis website, told AFP.
Syria's disintegration "is not a possibility, but a reality, and if the war ended tomorrow, it would take more than a decade for the country to recover", said Volker Perthes, director of the German Institute for International and Security Affairs.