U.N. chief Ban Ki-moon said on Wednesday Syria's crisis was highly alarming and had massive repercussions for the world, as heavy fighting raged in the Syrian capital Damascus.
We do not know how events will unfold. But we do know that we all have a responsibility to work for a resolution of this profound and extremely dangerous crisis, Ban said in a speech in the Indonesian capital Jakarta.
Syria lies in a pivotal position at the heart of a web of regional conflicts in the Middle East, comprising a mix of faiths, sects and ethnic groups, and diplomats fear the 12-month uprising is degenerating into a full-blown civil war.
Forces loyal to President Bashar al-Assad have made gains against rebels around the country in recent weeks, but the violence shows no sign of abating, with reports on Wednesday of several army offensives.
Opposition activists said the army turned tank, artillery and anti-aircraft guns on the Damascus suburbs of Harasta and Irbin on Wednesday, which were retaken from rebels two months ago but have seen renewed insurgency in recent days.
The suburbs are a linked series of towns inhabited mostly by members of Syria's Sunni Muslim majority, grown increasingly resentful at the domination of the Assads, who belong to the minority Alawite sect, an offshoot of Shi'ite Islam.
Elsewhere the army fired 11 mortar rounds into the Khalidiya district of Homs, the day after 14 people died in the same area from mortar attacks, the British-based Syrian Observatory for Human Rights said.
Artillery shells targeted the rebel town of Rastan, north of Homs city, in the centre of Syria, and Qalat Mudiq, northwest of Hama city, where an armoured personnel carrier came under fire. One soldier was killed in the attack, activists said.
Video footage showed shelling of the ancient Apamea castle at Qalat Mudiq. Reports from Syria cannot be independently verified because the authorities have barred access to rights groups and journalists.
Despite advances on the ground, Assad appeared to suffer a setback on the diplomatic front, with key ally Moscow adopting a new, sharper tone after months of standing by his government.
We believe the Syrian leadership reacted wrongly to the first appearance of peaceful protests and ... is making very many mistakes, Foreign Minister Sergei Lavrov told Russian radio station Kommersant-FM on Tuesday.
This, unfortunately, has in many ways led the conflict to reach such a severe stage.
Lavrov also spoke of a future transition period for Syria, but continued to reject calls from most Western and Arab states for Assad to resign, saying this was unrealistic.
It was not immediately clear if the change in tone would translate into a tangible difference in the way international powers, hitherto divided on Syria, might deal with the crisis.
The change in the Russian position is one of tone, not of substance. Moscow still sees its support of Assad as part of a regional game, but it is losing the support of the Syrian people, which could backfire on it if the Syrian regime falls, said Najati Tayyara, a prominent Syrian opposition figure.
The uprising started with mainly non-violent demonstrations last March, but the situation deteriorated rapidly in the face of a ferocious army crackdown.
Russia has previously vetoed two Western and Arab-backed U.N resolutions condemning government violence, arguing that the actions of rebels should also be criticised.
In an effort to secure Russian support for a new text, Western powers on the U.N. Security Council have diluted a draft statement backing U.N.-Arab League Syrian envoy Kofi Annan's drive to end the Syrian bloodshed.
The 15-nation panel held two rounds of negotiations on Tuesday on a statement that would express full support for Annan's peace efforts while threatening Damascus with further steps if it failed to comply with the council's demands in a timely manner, council diplomats told Reuters.
A previous version of the statement had threatened Syria with new U.N. measures if Damascus failed to comply within seven days, which diplomats said Russia considered to be an ultimatum. Moscow hinted it might back the new wording.
Annan dispatched a team of five experts to Damascus on Monday to discuss ways of implementing the peace drive, including a mechanism to let international monitors into the country. Syria has questioned the value of such a mission.
(Additional reporting by Oliver Holmes and Crispian Balmer in Beirut, Steve Gutterman in Moscow, Matt Spetalnick in Washington, and Olivia Rondonuwu in Jakarta,; Writing by Crispian Balmer Editing by Maria Golovnina)