A main opposition group says the death toll in Syria has risen to 50, including 30 in the battered city of Homs.
The activist group Local Co-ordination Committees gave the figures, but they could not immediately be confirmed by others.
The report comes as the Red Cross calls for a daily two-hour cease-fire nationwide so that emergency aid can reach beleaguered parts of the country.
Government troops heavily shelled rebellious districts in the resistance stronghold of Homs amid fears of a new round of bloody urban combat in a country careening toward all-out civil war.
The UN estimates that at least 5,400 people, most of them civilians, have been killed in the 11-month uprising against Syria's President Bashar Assad.
Taking an apparent peacemaking role, Russia urged the United Nations to send a special envoy to Syria to help co-ordinate security issues and the delivery of humanitarian assistance.
Russia proposes UN envoy
Russia's Foreign Ministry said on Twitter that it's proposing that the UN Security Council ask the UN Secretary General to send the envoy.
On Monday, Russia's UN Ambassador Vitaly Churkin said the world body should help solve humanitarian issues in Syria, after Damascus allowed the Red Cross to bring humanitarian aid to some regions.
International Committee of the Red Cross (ICRC) president Jakob Kellenberger called on Syrian authorities and rebels to agree immediately on a daily ceasefire of at least two hours to allow life-saving aid to reach civilians in hard-hit areas such as Homs.
"Over the past few days, we have been in contact with the Syrian authorities and members of the opposition to request this halt in the fighting," ICRC said in a statement calling for "an immediate decision to implement a humanitarian pause in the fighting."
Russia and China have vetoed two Security Council resolutions backing Arab League plans aimed at ending the conflict and condemning President Bashar al-Assad's crackdown on protests that killed 5,400 in 2011 alone, according to the UN Hundreds more have been killed since, activist groups say.
Syria is Russia's last remaining ally in the Middle East. Moscow has maintained close ties with Damascus since the Cold War, when Syria was led by the current leader's father, Hafez al=Assad.
Russian Foreign Ministry spokesman Alexander Lukashevich said Tuesday that Moscow will not attend the planned "friends of Syria" meeting at the end of this week, because its organizers had failed to invite representatives of the Syrian government.
Lukashevich said the meeting in Tunisia wouldn't help a dialogue, saying that the global community should act as friends of the entire Syrian people, and not just one part.
"It looks like an attempt to forge some kind of international coalition like it was with the setting-up of a 'contact group' for Libya," Lukashevich said.
Russia has said it will block any UN resolution that could pave the way for a replay of what happened in Libya. In that case, Russia abstained from a vote, which cleared the way for months of NATO air force attacks that helped Libyans end Moammar Gadhafi's regime.