Russian President Vladimir Putin stood firm on Friday against growing pressure over Moscow's position on Syria, opposing military intervention and raising doubts about the effectiveness of sanctions.

But as he met with German Chancellor Angela Merkel and French President Francois Hollande, Putin also warned the situation in Syria was 'extremely dangerous' and said he saw emerging signs of a civil war.

Putin struck his traditional fiery tone in a joint press conference with Hollande, saying 'sanctions hardly ever work in an efficient manner' and indicating that Bashar al-Assad's departure would not in itself resolve the crisis.

"Why are we thinking that if we push the current leadership from power, then tomorrow general well-being will begin there," Putin said.

"What is happening in Libya? What is happening in Iraq? Has it become safer there?" he said. "We propose to act in an accurate, balanced manner at least in Syria."

Hollande kept up the pressure however, insisting that Assad's departure was 'a prerequisite for a political transition' and that 'there must be sanctions' against his regime.

'Bashar al-Assad's regime has conducted itself in an unacceptable and intolerable manner. It has committed acts that disqualify itself' from governing, Hollande said.

The two seemed to establish a good working rapport, however, as Putin, on his first foreign tour since returning to the Kremlin, met the newly elected French leader for the first time.

In Berlin, Putin had warned of the escalating danger from the Syrian conflict.

"Today we are seeing emerging elements of civil war," he said after arriving 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.

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.

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'.

"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.

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.