Russia on Tuesday called the ceasefire in Syria "fragile" and urged countries to put more pressure on the armed opposition to cooperate with UN-Arab League envoy Kofi Annan's peace plan.

"The ceasefire really is relatively fragile," Russian Foreign Minister Sergei Lavrov told reporters in televised remarks.

"There really are those who are interested in the failure of Kofi Annan's plan and they actually mentioned that (opinion) even before this plan was made public," Lavrov said without naming specific countries.

Russia has previously condemned some Arab states for agreeing to provide funding to the opposition Free Syrian Army.

"There are countries, there are outside forces, that are not interested in the success of current UN Security Council efforts," Lavrov said.

- Agence France Presse