Russian President Vladimir Putin warned Friday of an "extremely dangerous" situation in Syria and emerging signs of a civil war but rejected a military intervention as he met with European leaders.
Amid mounting pressure for Moscow to drop its resistance to tougher UN action on Syria, Putin met with German Chancellor Angela Merkel and had arrived in Paris for talks with newly elected French President Francois Hollande.
In Berlin, Putin appeared to strike a more conciliatory tone, warning of the escalating danger from the Syrian conflict and refraining from openly backing President Bashar al-Assad's regime.
"Today we are seeing emerging elements of civil war," Putin said after arriving in Berlin from Belarus. "It is extremely dangerous."
But he also continued to defy calls for tougher UN action to stop the violence, warning at a joint press conference with Merkel: "You cannot do anything by force and expect an immediate effect."
And he hit back at suggestions Moscow was supplying weapons for use in the internal conflict, after the United States condemned Russian arms deliveries to Syria as "reprehensible".
"As far as arms supplies are concerned, Russia does not supply the weapons that could be used in a civil conflict," Putin told reporters, as he continued his first foreign tour since returning to the Kremlin.
Putin's brief trips to Berlin and Paris came amid mounting outrage in the West against Assad's regime after a massacre of 108 people, including women and children, in the town of Houla last week.
UN rights chief Navi Pillay said the massacre could be a crime against humanity.
In Moscow the foreign ministry blamed the Houla massacre on foreign assistance to Syrian rebels, including arms deliveries and mercenary training.
"The tragedy in Houla showed what can be the outcome of financial aid and smuggling of modern weapons to rebels, recruitment of foreign mercenaries and flirting with various sorts of extremists," the ministry said in a statement.
Putin said Russia, Germany and their partners would do their utmost to stop the violence from escalating and help UN-Arab League envoy Kofi Annan, who has brokered a peace plan for Syria, achieve "positive results".
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"We both made clear that we are pushing for a political solution, that the Annan plan can be a starting point but that everything must be done in the United Nations Security Council to implement this plan," Merkel said.
Putin said Moscow was not taking sides in the deadly strife rocking Syria, where the Britain-based Syrian Observatory for Human Rights says 13,000 people have been killed since Assad's regime launched a brutal crackdown on the opposition in March last year.
"There is a need to find a convergence of these interests and have them sit down at a negotiating table. That's the direction we are going to work in."
Merkel earlier greeted Putin with military honours as demonstrators waving Syrian flags shouted and whistled outside.
Putin was to hold a one-on-one meeting and dinner with Hollande, who has refused to rule out foreign military intervention as long as it is carried out with UN backing, followed by a press conference.
British Foreign Secretary William Hague also said Syria was on the verge of a civil war and risked collapsing into sectarian strife after meeting members of the Syrian opposition based in Istanbul.
Germany, France, Britain, the United States and other Western nations expelled Syrian diplomats in protest at the slaughter in Houla.
Syria allies China and Russia, which have both blocked previous attempts at the UN Security Council to condemn Damascus, joined other council members on Sunday in backing a statement condemning the Houla killings.
But US Secretary of State Hillary Clinton on Thursday warned that Russia's policy of propping up the Assad regime could contribute to a civil war and even lead to a wider proxy war because of Iran's support for Damascus.
And she claimed Friday that Russia had continued to supply arms to the Assad regime, raising "serious concerns" in the United States.
"We know there has been a very consistent arms trade, even during the past year, coming from Russia to Syria. We also believe the continuous supply of arms from Russia has strengthened the Assad regime," Clinton told a news conference in Oslo.
Amnesty International demanded that Putin immediately stop Russian weapons deliveries to Syria, while Human Rights Watch called on Putin to make human rights a priority at home and abroad.