Syrian forces blitzed areas in and around the northern city of Aleppo on Friday, activists said, as Western powers sought to tighten the screws on embattled President Bashar al-Assad.France said it backed 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 was due to meet UN chief Ban Ki-moon later Friday on the 17-month conflict that has escalated from a peaceful uprising against Assad's rule into an increasing bloody civil war.
France and Germany said they are pushing for UN Security Council action on the humanitarian crisis as the number of refugees soars above 200,000, while over 2.5 million are in need of aid inside the country, according to the UN.
The West has ramped up the pressure 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.
Syria's staunchest ally Iran meanwhile said it will submit a proposal for ending the conflict at a Non-Aligned Movement summit next week, saying it included "all parties" but gave no further details.
Activists reported heavy shelling by Syrian forces on several districts of Aleppo, scene of the fiercest fighting since the conflict first entangled the commercial and manufacturing hub a month ago.
Several houses were destroyed, the Syrian Observatory for Human Rights said, also reporting a bombardment on the town of Aazaz to the north.
At least 50 unidentified bodies were also found shot dead in the last 24 hours, notably in Aleppo and Damascus, it said, amid proliferating reports of summary executions.
Rebels said they were digging in for a war of attrition in Aleppo, where the regime had warned last month of "the mother of all battles" for the city.
"We don't have enough weapons, they (the Syrian army) don't have enough men," said Abu Haidar, a rebel fighter in the southwestern Saif al-Dawla district.
Both the government and opposition forces say 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 has dismissed the claims and said Thursday the army had recaptured three Christian neighbourhoods, where residents are largely pro-Assad.
Amnesty International warned Thursday that civilians were facing "horrific" violence in Aleppo as the regime waged indiscriminate attacks.
A UN panel earlier this month said the regime was guilty of crimes against humanity during the conflict, while also holding the rebels to task for committing war crimes, although to a lesser extent.
Regime forces also pounded several areas of 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.
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".
n Friday, activists reported that troops had stormed and shelled several areas including the town of Daraya which lies to the south of Damascus.
"Fear is everywhere," said a Damascus resident and anti-regime activist who gave her name as Samara.
A total of 149 people were killed on Thursday alone, including 14 children, the Observatory said.
Around 24,500 people have been killed since the uprising erupted in March last year -- with August already the bloodiest month, according to Observatory director Rami Abdel Rahman.
The UN puts the death toll at more than 17,000.
The Local Coordination Committees, a large activist network, said meanwhile that prominent Syrian film producer Orwa Nyrabia had disappeared and was feared arrested, but its report could not be confirmed independently.
Amid a flurry of diplomatic moves on the crisis, France said it would consider backing a partial no-fly zone, a proposal being studied by Washington, although US Defence Secretary Leon Panetta said Wednesday it was "not on the frontburner right now."
French Defence Minister Jean-Yves Le Drian however 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.
Ahead of the Brahimi-Ban meeting, Syria's deputy foreign minister Faisal Muqdad said Damascus was ready to work with the new envoy and voiced hope he could pave the way for "national dialogue."
Another minister said this week the regime was "ready to discuss" Assad's departure as part of any negotiated solution but the West is insisting the man who has ruled Syria with an iron fist for 12 years must go now.
The Security Council has so far failed to agree how to tackle the crisis because of divisions between the West and Syria's traditional allies in Bejing and Moscow, and last weekend wrapped up its troubled observer mission.
Neighbouring Lebanon was rattled again Friday by new fighting between rival pro-and anti-Damascus communities in the northern port city of Tripoli, with 13 people killed since Monday, adding to fears of a spillover of the Syria conflict.