Syrian troops pushed towards the Lebanese border as they pressed a deadly crackdown in central towns ahead of Monday's opposition meeting in Damascus on the country's unrest, activists said.
The latest violence in Kseir, near the flashpoint city of Homs, forced "hundreds" of people to flee over the border into Lebanon, the activists said.
The exodus came as Turkey, where about 12,000 Syrians have already taken refuge in recent weeks, scrambled to erect a border tent city to accommodate a possible new influx of refugees.
Rami Abdel Rahman, who heads the London-based Syrian Observatory for Human Rights, told AFP in Nicosia that shots rang out in Kseir -- 15 kilometres (nine miles) from the border with Lebanon, and in Homs.
He said on Saturday, "hundreds of residents fled from Kseir to Lebanon."
Four civilians were shot dead by security forces on Saturday, two in Kseir and two in Kiswah, south of the capital.
Activists say that security forces have bolstered their presence in Kseir since Friday, while troops have been controlling areas of Homs for several days, as part of a policy to crush pro-democracy protests.
The sweep against the opponents of the autocratic regime of President Bashar al-Assad has also seen troops backed by tanks storm villages near the border with Turkey.
French Foreign Minister Alain Juppe said Sunday that Assad had passed the "point of no return.
"I would be happy to admit I'm wrong, but I don't think so," he he told France's RTL radio.
"I regret that the repression continues to unfold in conditions which calls into question the region's security, because we have reached more than 10,000 refugees in Turkey...," Juppe added.
On Saturday, tanks rumbled into Al-Najia, after similar operations in Jisr al-Shughur, seized on June 12, and Khirbet al-Joz, where troops deployed on Thursday, according to activists.
Pro-government daily Al-Watan said Khirbet al-Joz was used as a "key crossing for armed groups from and to the Turkish" border. The army was "now cleansing" the village of any armed presence, securing roads and protecting residents.
And state news agency SANA said families were returning from Turkey to Jisr al-Shughur on Sunday for the second day in a row.
"Almost 730 people have returned... They had fled from the terror of the terrorist groups in the region," it said.
In Lebanon, however, a village headman said that hundreds of people, mostly Lebanese living in Syria, had sought safe haven in the northern Akkar region over the weekend.
Around 350 to 400 people streamed into Kuneissat on Friday and Saturday, said the headman of the Lebanese border village, Ali Hammud, adding that most came from Al-Hit and Dweik villages and some from Kseir.
Anti-government protests in Syria swelled on Friday with tens of thousands of people surging onto the streets in response to Syrian Revolution 2011 -- a Facebook group and driving force behind three months of demonstrations.
Security forces used live ammunition and tear gas against the protesters, killing 18 people and wounding scores more, activists told AFP. Funerals were held on Saturday for the victims.
Opposition figures are due to meet in Damascus on Monday on ways to solve the crisis which has gripped Syria since mid-March.
"We will talk so that we can formulate a national strategy on how to end Syria's current crisis," Abdel Karim Rihawi, president of the Syrian League for Human Rights, told AFP.
But the one-day grouping of more than 100 independents, with no ties to political parties, will not take the place of "protesters in the street," the rights activist stressed.
Anwar Bunni, a prominent rights lawyer who has spent five years in Syrian jail, played up its significance as "a first meeting of its kind at a public venue announced in advance."
The opposition will only take part in a "national dialogue" as proposed by the authorities if peaceful demonstrations are authorised, political prisoners are released, the opposition recognised and the use of force halted, he told AFP.
Syria's military spokesman Major General Riad Haddad, quoted on CNN, said 1,300 members of the security forces have been killed in the revolt, in attacks which the authorities have blamed on "armed gangs."