BEIRUT — U.N. observers suspended their patrols in Syria on Saturday due to a recent spike in violence, the strongest sign yet that an international peace plan was unraveling despite months of diplomatic efforts to prevent the country from plunging into civil war.

The U.N. observers have been the only working part of a peace plan brokered by international envoy Kofi Annan, which the international community sees as its only hope to stop the bloodshed.

The plan called for the foreign patrols to monitor compliance with a cease-fire taking effect on April 12, but they have become the most independent witnesses to the carnage on both sides as government and rebel forces have largely ignored the truce.

Maj. Gen. Robert Mood, the U.N. mission chief, said intensifying clashes over the past 10 days were “posing significant risks” to the 300 unarmed observers spread out across the country and impeding their ability to carry out their mandate.

The observers will not leave the country but will remain in place and cease patrols, Mood said in a taped statement, adding the suspension would be reviewed on a daily basis. Teams have been stationed in some of Syria’s most dangerous cities, including Homs and Hama.