Russia accused Friday that "certain elements" in Syria are trying to derail UN-Arab League joint envoy Kofi Annan's peace plan.

"Certain elements is provoking the country's authorities....to undermine the plan of the special envoy of the UN and the Arab League to Syria, Kofi Annan, and launch the spiral of violence once again," spokesman of the Foreign Ministry Alexander Lukashevich said.

He admitted that the situation in Syria remained "highly complicated", despite the deployment of the UN observers.

"The direct armed clashes between the army and illegal armed groups have been replaced by growing terror activities," Lukashevich warned.

He pointed out that some representatives of the Syrian opposition were not going to implement Annan's plan, calling on all countries that support Annan's plan to strictly adhere to it.

"The ultimate goal of the plan is to stop the confrontation and launch a political process led by the Syrians themselves," he said.

Meanwhile, Lukashevich did not rule out that the UN mission to Syria could be expanded.

Still, he denied the UN observers would be armed.

"High on the agenda is an acute issue of the observers' mobility, and the creation of a certain helicopter group to provide UN observers with their own transport for free movement on the Syrian territory," Lukashevich said.