DAMASCUS, Syria -- The Syrian army captured a strategic town near the Lebanese border on Wednesday after a grueling three-week battle, handing a heavy defeat to rebels and solidifying a shift in the country's civil war in favor of President Bashar Assad's regime.
Both sides had dug in for an all-out battle for Qusair, which rebels seized last year, a sign of its importance for both as a key crossroads of supply lines between Damascus and western and northern Syria. The regime assault also marked another key turning point in the conflict: the most overt involvement yet by its Lebanese Hezbollah allies, whose fighters boosted the military's firepower in overcoming the rebels.
The town's fall could boost the momentum for Syrian troops in rolling back rebel gains in central Syria in past months. The blow to the rebel movement could also further discourage it from entering peace negotiations with the regime, which the United States and Russia have been trying to put together in Geneva.
In a rare statement read on state TV Wednesday, the Syrian military triumphantly declared that it had "cleansed" Qusair of rebels. It said the town's capture was a "clear message to all those participating in the aggression against Syria" -- a sign clearly directed at the rebels' regional backers that the regime believes the tide is turning in the war.
Images broadcast by media embedded with Syrian troops showed a deserted town with heavily damaged buildings and the Syrian flag flying over a clock tower in its main square. Syrian soldiers celebrated atop rubble, waving Syrian flags and chanting pro-regime slogans. Military bulldozers were removing rubble and clearing roads as armored vehicles whizzed by.
Outnumbered and outgunned, rebel fighters held out for weeks after the regime launched its assault on Qusair on May 19. They inflicted heavier than expected casualties on the Hezbollah forces who joined the battle, forcing the group to admit its involvement as dozens of its fighters were brought home for burial. As fighting intensified, rebels called on fighters from all over Syria to come to their aid, and foreign militants were suspected to be playing a large role in the town's defense.
But the rebels were running short of ammunition, and they finally withdrew from the town after an intense bombardment overnight, according to the Syrian Observatory for Human Rights, a Britain-based opposition activist group.
"The Assad regime and the Iranian militias supporting it have entered Qusair," a statement by the main Western-backed Syrian National Council said, lamenting the "enormous imbalance in the balance of power."
During the barrage, doctors in the town managed to evacuate some 300 seriously wounded civilians who had been trapped during the siege. Convoys ferried them to the nearby village of al-Buweida, the doctor who had been coordinating medical treatment in Qusair, Kazem Alzein, said on Skype.
"We had to. They were destroying the neighborhood," he said.
"The town is empty," one witness in the town told The Associated Press by telephone, speaking on condition of anonymity because he feared for his security.
The mainly Sunni town -- formerly home to some 40,000 people -- was key for both sides. It lies on a land corridor linking two Assad strongholds, the capital of Damascus and an area along the Mediterranean coast that is the heartland of his minority Alawite sect.
For the rebels, who controlled the town since early 2012, Qusair was part of a supply line to Lebanon, serving as a conduit for weapons, fighters and supplies smuggled from Lebanon to the rebels inside Syria.
Capturing Qusair could open the way for the regime's troops to move on rebels in other parts of central Homs province.
On the ground in the past two months, the Syrian army has moved steadily against rebels in key battleground areas, making advances near the border with Lebanon and considerably lowering the threat to Damascus, the seat of Assad's government.
"The (army's) general command reaffirms that its battle against terrorism will continue until peace, security and stability is restored to every inch of Syrian land," the military said in its statement, employing the term the regime uses for rebels fighting to topple Assad.
The fall of Qusair provides the best evidence to date that the growing participation of militant Hezbollah fighters alongside Assad's troops is a potential game changer in the Syrian two-year-old conflict.
The Shiite group, which has been fighting alongside Assad's troops, initially tried to play down its involvement. But during the offensive, Hezbollah's leader Hassan Nasrallah firmly linked the group's fate to the survival of the Syrian regime, raising the stakes not just in Syria, but also in Hezbollah's relations with rival groups in Lebanon.
In Hezbollah's strongholds of southern Beirut, celebratory gunfire and fireworks erupted as news of Qusair's capture was announced and continued sporadically for two hours. The group's supporters put up yellow Hezbollah flags along with small banners on street isles that read: "Qusair has fallen," as people in the streets distributed sweets to passers-by.
In the northeastern Lebanese town of Bazzalieh, near the city of Baalbek, Hezbollah supporters set up a check point on a main road distributing sweets to people in celebration. "Today, we defeated the other Israel," said Ali al-Bazzal, 23, while waving a yellow Hezbollah flag.
But Hezbollah's overt involvement has increased the Syria conflict's slide toward a regional sectarian conflict. The war already risks spilling over into Lebanon, where Sunni-Shiite tensions have mounted and Syrian rebels have retaliated against Shiite towns near the Syrian border.
Qusair's fall risks drawing further revenge attacks.
"The repercussions will be on the Lebanese territories," Bassam al-Dada, an official in the rebels' Free Syrian Army, told The Associated Press. "It is the beginning of the end for the group, even inside Lebanon," he added.
George Sabra, acting head of the main Western-backed Syrian National Coalition, said the battle for Qusair was just "one round" in a larger fight to "liberate Syria."
At a press conference in Istanbul, he slammed Iran and Hezbollah's "murderous" involvement and warned Hezbollah's role in Syria will deepen the Sunni-Shiite rift in the region.
The shifts on the battlefield further complicate possibilities for peace talks that the United States and Russia are trying to convene in Geneva. Assad's regime has agreed in principle to attend, but the opposition has balked, saying it won't participate while "massacres are taking place"
On Wednesday, U.N.-Arab League envoy Lakhdar Brahimi acknowledged that "the opposition has to complete a lot of work to get ready for this conference ... And until the opposition is ready, all we can do is wait."
He told reporters in Geneva that a conference is unlikely to take place before July, admitting, "it is embarrassing for us that we are not capable of holding this conference all ready."
A day earlier France and Britain made back-to-back announcements that the nerve gas sarin was used in Syria's conflict. A U.N. probe, also released Tuesday, said it had "reasonable grounds" to suspect small-scale use of toxic chemicals in at least four attacks in March and April in Syria.
The statements -- which included a confirmed case of the Syrian regime using sarin -- leave many questions unanswered, however, because the probes were mostly carried out from outside Syria from samples collected by doctors and journalists.
In the West, the lack of certainty about such allegations is linked to a high stakes political debate over whether the U.S. should get more involved in the Syrian conflict, including by arming rebel fighters. More than 70,000 people have been killed and several million displaced by the Syrian conflict since it erupted more than two years ago.