HELSINKI - The United Nations Security Council alone can authorize the use of force against Syria, Russian Foreign Minister Sergei Lavrov said on Monday, warning against what he called imposing "democracy by bombs."Lavrov's warning against intervention comes as Syria's 17-month uprising against President Bashar Assad grinds on with no sign of a ceasefire and as the United States and others consider what further steps they can take to end the bloodshed.Lavrov has said Moscow would not approve any political transition that was forced on Syria.UN military observers left Damascus on Monday after a four-month mission.At least 18,000 people have now been killed in Syria since the anti-Assad revolt began, and at least 170,000 people have fled the country, according to the United Nations.'Syrian rebels getting lots of Western arms'Earlier Monday, Russia cited what it called increasing evidence that Syrian rebels were obtaining large amounts of Western-made arms, suggesting the United States and European countries are helping fuel persistent violence in the divided country.Deputy Foreign Minister Gennady Gatilov's comments echoed others that appear intended to blame Western and Arab countries for the failure to end the conflict through diplomacy such as outgoing mediator Kofi Annan's peace plan."There is growing evidence, including in the media, that Syrian opposition is massively supplied with Western-made weapons through third countries," Gatilov wrote on his Twitter microblog. He did not provide details.The United States and Britain say they are providing non-lethal assistance to rebel such as communications equipment but not arms. Saudi Arabia and Qatar, two strong Arab opponents of Assad, are believed to be funding a flow of weapons to rebels."We find it appropriate to defend the UN Charter that states the use of force can be only be decided by the Security Council," Lavrov said in a speech in Helsinki, where he was meeting Finnish government leaders."Syria's situation is important and causing worry not only because of the bloodshed but also because the outcome of this drama will impact the way conflicts will be resolved; either following the UN Charter, or democracy by bombs, will win."Russia has consistently defended Assad at the United Nations, blocking sanctions against him and ruling out the use of outside force to end the conflict. It has also supplied his government with arms, while complaining that Syrian rebels are receiving large amounts of Western-made arms.