Syrian troops infiltrated Tuesday into northern and eastern parts of the Lebanese territories and set up fixed posts to prevent Syrians from escaping into Lebanon, a Lebanese security source told dpa.
"The incursion is the third since last month," the source said.
Last week, Syrian troops were seen planting landmines along the northern and eastern border with Lebanon.
The source said the Syrian army planted most of their landmines near Lebanon's northern border to prevent what they described as arms smuggling into the flashpoint province of Homs where armed clashes were reported over the past week between army deserters and government troops.
Since the uprising in Syria started against the regime of President Bashar al-Assad in mid-March, some 5,000 refugees, among them army deserters, have fled into northern and eastern Lebanon.
The source, who requested anonymity for security reasons, said the Syrian government is working with its allies inside Beirut to prevent Lebanon from becoming a safe haven for opposition.
Lebanon's political arena is split between supporters of al-Assad, led by Hezbollah, and a pro-Western camp headed by former premier Saad Hariri.
A member of the Hariri parliamentary bloc, Imad al-Hout, said Tuesday that the recent Syrian incursions into Lebanese territory "violate human rights charters."
"The Lebanese government must safeguard its sovereignty."
The crackdown by al-Assad's regime on pro-democracy protests has left at least 3,000 people dead since mid-March, according to UN figures.