Syrian forces blitzed areas in and around the city of Aleppo Friday, destroying a number of homes, activists said, as Western powers sought to tighten the screws on strongman Bashar Al-Assad.
France voiced support for a partial no-fly zone over Syria, where the regime is intensifying its attacks from the air as it battles to stamp out rebel strongholds in Aleppo and pockets of resistance in the capital Damascus.
New envoy Lakhdar Brahimi is due to meet UN chief Ban Ki-moon later Friday to discuss the 17-month conflict that has escalated from a peaceful uprising against Assad's rule into an increasing bloody civil war and triggered a major humanitarian crisis.
Turkish and US officials also held their first "operational planning" meeting Thursday on ways of bringing down the regime, while Italy said it is planning to host international talks in the next few days on a post-Assad Syria.
Syria's staunchest ally Iran said it will submit a proposal for ending the conflict at a Non-Aligned Movement summit next week, but gave no details.
The West has ramped up the pressure on Damascus as the fighting grinds bloodily on into its 18th month, with the United States and Britain warning Damascus of possible action if it resorts to its chemical weapons arsenal.
Activists reported heavy shelling Friday by Syrian forces on several districts of Aleppo, scene of the fiercest fighting since the conflict first entangled Syria's commercial and manufacturing hub a month ago.
Several houses were destroyed in the bombardment, the Syrian Observatory for Human Rights said, also reporting shelling on the town of Aazaz to the north.
Regime forces also pounded several areas in the largely rebel-held province of Idlib in the northwest, the Observatory said, while fierce fighting erupted between rebels and troops in the central province of Hama.
Both the government and opposition forces say the attacks on Aleppo province are aimed at cutting arms supply routes to the rebels in Syria's second city, once a thriving metropolis of 2.7 million people but now largely in ruins.
Rebels claimed earlier this week to control 60 percent of Aleppo but the regime said Thursday the army had recaptured three Christian neighbourhoods, where residents are largely pro-Assad.
Government troops have also waged ferocious onslaughts on the southern outskirts of Damascus over the past two days in what activists said was a renewed bid to crush the insurgency in the capital "once and for all".
Residents and activists reported shelling and fighting from the southwestern district of Al-Hajar Al-Aswad to the town of Daraya on the western outskirts of the capital Thursday, while regime forces also launched house-to-house raids.
"Parts of Damascus look like Gaza, with the army deployed on the outside, setting up major checkpoints, but unable to get in," said a Damascus resident and anti-regime activist who gave her name as Samara. "Fear is everywhere."
A total of 149 people were killed on Thursday, the majority of them civilians and including 14 children, the Observatory said, also reporting the discovery of dozens of unidentified bodies in Aleppo and Damascus.
It said around 24,500 people have been killed since the uprising against Assad's rule erupted in March last year, while the UN puts the death toll at 17,000.
Underscoring the increasingly brutal nature of the conflict, Amnesty International said Thursday that civilians were facing "horrific" violence in Aleppo, and accused the regime of waging indiscriminate attacks.
Even as the fighting raged, Syria's deputy foreign minister Faisal Muqdad said Damascus was ready to work with Brahimi and voiced hope that he could pave the way for "national dialogue."
Another minister this week said the regime was "ready to discuss" Assad's departure as part of any negotiated solution to the conflict but the West is insisting the man who has ruled Syria with an iron fist for 12 years must go now.
"There will be no winners in Syria, as the West is betting there will be. Syria will win, thanks to its people, its leader and its government, which will make the right choices in the midst of these difficult circumstances," Muqdad said.
He charged that the conflict was being fuelled by armed "terrorist groups" backed by countries including neighbouring Turkey.
Turkey, a one-time Damascus ally, has repeatedly denied giving arms to the rebels but has given sanctuary to the defecting soldiers who formed the kernel of the Free Syrian Army as well as to tens of thousands of civilian refugees.
While Turkish and US officials held their first "operational planning" meeting Thursday aimed at hastening the end of Assad's regime, the German and French leaders were pushing for a UN Security Council decision on the increasingly precarious humanitarian situation.
At least 170,000 people have fled, while another 2.5 million are in need of aid within Syria, according to the UN.
France also said it would consider supporting a partial no-fly zone over Syria, a proposal being studied by the United States, although US Defence Secretary Leon Panetta said Wednesday it was "not on the frontburner right now."
French Defence Minister Jean-Yves Le Drian warned that shutting all of Syria's air space would mean "going to war" and would require a willing international coalition that has not yet materialised.
The UN Security Council has failed to agree on any action to end the conflict, hampered by rifts between the West and Damascus's traditional allies in Russia and China.