Syrian security forces have kept heavy weapons in cities in breach of Annan's peace plan, but the government and opposition both have committed truce violations, a top UN official said on Tuesday.

The 34 unarmed military observers now in Syria have seen Howitzer guns, armoured personnel carriers and other weaponry in cities, UN peacekeeping chief Herve Ladsous told reporters.

Ladsous insisted, however, that the monitors were having an effect in cities where they have been allowed to go.

"Regarding the heavy weapons, yes, our military observers do see a number of APCs, for instance, they see a number of Howitzers and other military equipment in most places where they are," Ladsous said.

Syria has told the monitors that the armored carriers have been disarmed but this has not been verified, Ladsous added.

Ladsous said both government forces and opposition groups have broken the truce.

"All the parties need to take further steps to ensure a cessation of violence in all its forms," he said. "The important fact is that violations do come from both sides." [AFP]