BEIRUT — Syrian troops and rebel gunmen carried out attacks across Syria on Saturday, killing at least nine people in a surge of violence that threatened a U.N.-brokered cease-fire.

The bloodshed came as the U.N. Security Council considered whether to send the first wave of military observers to monitor the fragile truce between the two sides.

The heaviest fighting was reported in the central city of Homs where regime forces shelled rebel-held neighborhoods, while rebel fighters fired rocket-propelled grenades at an area of regime loyalists. In Aleppo, Syria’s largest city, regime forces opened fire on mourners at a funeral, while rebel gunmen ambushed a car carrying soldiers in the southern province of Daraa.

The two sides have traded allegations of scattered violations since the truce formally took effect Thursday. However, Saturday’s reports of the use of heavier weapons suggested the cease-fire was coming under increasing jeopardy.

The cease-fire is at the center of a broadly backed peace plan by special envoy Kofi Annan. It is aimed at ending the 13-month-old conflict that has killed over 9,000 people and launching talks on the country’s political future.