Damascus - Syrian forces bombarded Aleppo with barrel bombs and air raids for a second day on Sunday, with scores of people killed in 48 hours, a monitor said, after peace talks ended inconclusively.
At least 36 people were killed in Sunday's attacks alone on Syria's second city, the Syrian Observatory for Human Rights said, after reporting 85 deaths the previous day.
Saturday's toll was one of the bloodiest in weeks and reflects the deep divide between the government of President Bashar Assad and his opponents despite 10 days of peace talks.
The nearly three-year-old conflict erupted into a fully fledged war after a crackdown on anti-government protests in the wake of Arab Spring uprisings that toppled veteran presidents.
More than 136 000 people have been killed in Syria since the conflict began, with January one of the bloodiest months, and millions have been displaced internally and as refugees in neighbouring countries.
The war has also spilled over into Lebanon, sparking sectarian clashes between supporters and opponents of the Syrian government as well as deadly car bomb attacks.
On Sunday, government warplanes pounded rebel-held districts in eastern Aleppo, with helicopters dropping the controversial makeshift barrel bombs denounced by rights groups as indiscriminate.
Observatory director Rami Abdel Rahman told AFP that 21 people were killed in three waves of barrel bomb attacks on the Tareq al-Bab district, including 13 children.
Another 15 died in separate air raids and barrel bomb strikes on the divided city.
On top of that at least 16 Syrian rebels were killed in a double bomb attack carried out by the jihadist Islamic State of Iraq and the Levant, the NGO said.
Another 20 rebels were wounded, some of them seriously, in the attack in the town of al-Ra'ei, not far from the Syrian border with Turkey, the Observatory added.
The rebels were Islamist brigades that have joined moderate rebels in fighting the jihadist Isil since the beginning of a backlash in early January.
The Observatory said the bomb attack came as fighters gathered at an Islamist rebel brigade headquarters to discuss the possibility of a truce in the fighting with Isis that has raged throughout rebel-controlled areas.
Once Syria's economic hub, Aleppo is now split into government- and rebel-held areas, with large swathes of the city devastated by the fighting that began there in mid-2012.
Over the past weeks Assad's forces have been advancing in the area around the city, in a bid to rout out the rebels.
Al-Watan newspaper reported on Saturday that government troops had seized control of most of the east Karam al-Turab district - which the Observatory confirmed.
The newspaper said troops were trying to win control of several eastern and northern districts in Aleppo, buoyed by their capture of the area around its airport late last year.
The airport reopened to traffic in January after being closed for nearly a year by fighting.
Defence Minister General Fahd al-Freij toured liberated areas in Aleppo province on Friday and praised the army for its "great victories", state news agency Sana reported.
Al-Watan also reported military operations under way near the town of Zara in central Homs province bordering Lebanon. The Observatory confirmed fierce fighting around Zara.
Opposition sank talks
With violence raging unabated, Deputy Foreign Minister Faisal Muqdad blamed the opposition for the failure of peace talks in Switzerland that ended on Friday with no tangible result.
Sana quoted Muqdad who described the opposition as "mercenaries manipulated by foreign forces" - a reference to Western and Arab countries that back Assad's opponents.
Representatives of the Syrian government and the opposition held 10 days of talks that failed even to meet the primary goal of allowing humanitarian access into besieged areas, mainly the Old City of Homs.
Western nations are now planning a UN Security Council resolution on the issue and possibly on the slow pace of a programme to move Syria's chemical weapons out of the country.
Despite not being on the agenda at the talks, aid has entered the besieged Palestinian refugee camp of Yarmuk on the outskirts of Damascus, and hundreds of the estimated 18 000 residents trapped inside were allowed to leave.
The UN agency for Palestinian refugees, UNRWA, has distributed more than 3 000 food parcels since it gained entry to Yarmuk in mid-January.