Long columns of Syrian troops crossed the border from Lebanon ahead of a visit to Damascus by UN Middle East envoy Terje Roed-Larsen.
Crowds threw flowers at troops returning to Syria
An undisclosed number of the 6,000 troops deployed in Lebanon's Bekaa Valley crossed into Syria in a convoy.
Mr Roed-Larsen will meet Syrian leader Bashar al-Assad this weekend to press for a timetable for a full withdrawal.
The UN has called for the immediate withdrawal of all 14,000 Syrian troops and intelligence personnel.
The BBC's Dan Isaacs on the Syria-Lebanon border says crowds of government supporters were bussed to the frontier for a carefully stage-managed occasion.
Troops came out of the night and through heavy snow, and had flowers thrown by crowds as they passed by.
SYRIA IN LEBANON
Military intervention begins in 1976
30,000 troops in Lebanon during 1980s, currently 14,000
Syrian forces help end Lebanese civil war in 1990 and maintain peace
Calls for Syrian withdrawal increase in 2000 after Israeli pullout from southern Lebanon
UN resolution calling for foreign forces' withdrawal in Sept 2004
By late on Friday the Syrian army had evacuated all its positions in northern Lebanon except for six known intelligence positions, the AFP news agency reported Lebanese sources as saying.
About 60 vehicles passed through the border overnight, including a range of covered trucks, along with buses and jeeps.
Washington reacted by calling for complete Syrian withdrawal.
State Department spokesman Richard Boucher said:"[UN]Resolution 1559 says immediate and full withdrawal. That's what we are looking for.
"We are looking for action from Syria. We are not looking for excuses or rhetoric," Boucher underlined.
In Damascus, Mr Roed-Larsen will press President Assad to adhere to a UN resolution, passed on 2 September last year, that calls for the complete withdrawal of all Syrian troops from Lebanon.
Syria has stationed troops in Lebanon since 1976, when it was asked to intervene by one of the factions fighting in the civil war.
"I'm looking forward for a good dialogue and of course I expect that we will get commitments and timetables for a full implementation of Resolution 1559," Mr Roed-Larsen said on Friday.