The chief of UN observers in Syria has said their mission is being suspended because of escalating violence in the country.
Major General Robert Mood said that the continued bloodshed is posing significant risks to the observers during patrols and is impeding their ability to carry out their mandate.
He said the observers will not be conducting patrols and will stay in their locations in the country "until further notice". The suspension will be reviewed on a daily basis.
The move is the latest sign that a peace plan brokered by international envoy Kofi Annan is disintegrating.
The Syrian regime under president Bashar Assad and the opposition have both ignored the ceasefire, which was supposed to go into on effect April 12.
The 300 unarmed observers were sent to the country after international envoy Kofi Annan brokered the peace plan.
The Syrian government, intent on regaining control of rebel-held areas, has launched a fierce offensive in recent days to recover territories in several locations, shelling heavily populated districts and using attack helicopters over towns and cities.
UN officials have said that the opposition, in turn, is increasingly co-ordinating attacks against government forces and civilian infrastructure.
On Saturday, government troops kept up their relentless shelling of rebel-held districts in the central city of Homs, killing at least five. Another 12, including a man, his wife and child, were killed in overnight shelling of suburbs of the capital Damascus.
Maj Gen Mood said: "Operations will resume when we see the situation fit for us to carry out our mandated activities."