Syrian troops and rebels have clashed in the city of Aleppo, amid reports that several people have died after a shell crashed into a bakery as residents queued for bread.
AFP news agency correspondents said that around a dozen people, including three children, were killed and 20 people were wounded on Friday at the bakery, in the eastern Tariq al-Bab district of Syria's second largest city.
Elsewhere, government forces repelled a rebel attack on Aleppo's international airport, state news agency SANA reported.
"Mercenary terrorists" had tried to attack it but the "army hit back and killed most of them", it said.
In the latest clashes, Aleppo's historic Citadel, part of a UNESCO-listed world heritage site, was heavily damaged by bombing, the opposition said.
The International Committee for the Red Cross (ICRC) said the Syrian Red Crescent had suspended most of its work in Aleppo because of the extreme danger.
A statement in Geneva said the ICRC had managed on Thursday to deliver food and other essential to cover the needs of at least 12,500 people in the city of some 2.7 million people.
'Holding on Salaheddin'
A rebel commander, Hossam Abu Mohammed, said his men were still fighting in parts of Aleppo's southwestern district of Salaheddin after most fled on Thursday in the face of heavy bombing and advancing troops.
"We will not let Salaheddin go," Abu Mohammed of the Free Syrian Army (FSA) told AFP by telephone on the third day of a government offensive to take the city.
And one of the fighters told AFP the rebels were keeping at bay troops who control a key roundabout from advancing further into Salaheddin.
"They have a few soldiers at the roundabout and some snipers. What we are doing now is preventing the troops from advancing," the fighter said on condition of anonymity.
In-depth coverage of escalating violence across Syria
The army again bombed parts of Salaheddin, as well as the Sakhur and Hanano districts in the northeast, the Syrian Observatory for Human Rights (SOHR), the UK-based watchdog, said.
At least 82 people were killed nationwide on Friday, including 35 civilians, it said. One of those killed was a 19-year-old protester shot dead by regime forces in Aleppo.
Before dawn, a MiG 21 fighter jet dropped four bombs on rebel positions in Hanano, an AFP correspondent said.
One struck the courtyard of an FSA compound and another struck a nearby house, wounding a number of people.
Angry residents shouted hostile slogans against France and the US, saying: "No one is helping us."
"We are behind the Free Syrian Army, but it is because of them that all of this is happening," one of them lamented.
The opposition Syrian National Council said Aleppo's 13th-century Citadel, part of a complex of sites in the city's historic heart that the UN Educational, Scientific and Cultural Organisation says is of "outstanding universal value" had been damaged in army shelling.
It was not possible to independently verify the opposition's claim.
Also on Friday, rebels captured three journalists who work for Syrian state television as they accompanied government troops operating near Damascus, the SOHR said.
The violence raged on as world powers prepared to name Lakhdar Brahimi, a veteran Algerian diplomat, as their new envoy to seek an end to a 17-month uprising that has cost more than 21,000 lives.
Diplomats at the UN said Brahimi was expected to be named early next week.
Negotiations were still under way over the envoy's role and how the UN will operate in Syria amid the intensifying civil war.
The mandate of the UN mission in the country ends on August 20.
Kofi Annan, a former UN secretary-general, resigned from the post of envoy, saying he had not received enough international support for his efforts to end the conflict but is staying on until August 31.
In a statement released by The Elders, a group of world statesmen, Brahimi said "the UN Security Council and regional states must unite to ensure that a political transition can take place as soon as possible.
"Millions of Syrians are clamouring for peace. World leaders cannot remain divided any longer, over and above their cries".
New US sanctions
The US, meanwhile, imposed fresh sanctions on President Bashar al-Assad's government and on the Lebanese Shia group Hezbollah, a close ally of Syria and Iran.
"This kind of trade allows Iran to continue developing its nuclear programme while providing the Syrian government with resources to oppress its own people," Patrick Ventrell, US state department spokesman, said.
In a bid to starve the regime of much-needed revenue, the US imposed sanctions on the Syrian state oil marketing company Sytrol on Friday for trading with Iran.
And the US treasury said it was adding Lebanon's Hezbollah to a blacklist of organisations targeted under Syria-related sanctions.
"Iranian officials have boasted about Iran's support to Assad," Ventrell said.
"Iran's actions in Syria underscore its fear of losing its only remaining ally in the Middle East and an important conduit to Hezbollah."
Separately, Britain said on Friday it would give the rebels five million pounds ($7.82m) in non-lethal assistance, including body armour and communications equipment.
"The people of Syria cannot wait indefinitely, people are dying. In the absence of diplomatic progress the UK will do much more," William Hague, UK foreign secretary, said.