Such a major battlefield success for President Bashar al-Assad's forces, if confirmed, would come as officials from Russia, the US and the UN gathered in Geneva to work on a peace conference amid fresh allegations that the Damascus regime has used chemical weapons.
"The Syrian army totally controls the Qusayr region in Homs province after killing a large number of terrorists and capturing others," state television report said, using the regime's terminology for the rebels.
Assad forces and Hezbollah fighters launched an offensive to retake the Qusayr region on the Lebanese border, on May 19.
Rebels fighting to retain control of the town, only some 10 kilometres from the frontier, were later joined by hundreds of reinforcements from Lebanon, most close to the Muslim Brotherhood. That lead to pitched battles in which civilians, many of them wounded, became trapped.
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Doctors had appealed for the Red Cross to be allowed in to treat the wounded, but Syrian officials said this would only be permitted once the rebels had been defeated.
Those who had escaped were mainly women and children, because men risked being killed at checkpoints, said spokeswoman Melissa Fleming.
Control of Qusayr is vital for the rebels as it is their principal transit point for weapons and fighters from Lebanon.
It is also strategic for the regime because it is located on the road linking Damascus with the coast, its rear base.
On the diplomatic front, officials meeting in Geneva hope to hammer out terms to get Assad's camp and the rebels to negotiate directly for the first time.
Earlier, a UN report said there were "reasonable grounds" to believe that both sides in Syria had used chemical weapons.
However, Washington said it needed more evidence before concluding that sarin had been used.