There has been heavy fighting in Syria's biggest city of Aleppo, with state media saying rebels have suffered big losses in their latest assault.
Rebel commanders had announced a major offensive on Friday to secure control of the whole of the city.
Both sides reported clashes across Aleppo but state media said counter-attacks had inflicted heavy losses.
Activist groups say 150 people were killed across Syria on Friday, 40 of them in Aleppo.
The signs are that the rebels simply lack the firepower and the manpower to score a significant breakthrough, the BBC's Jim Muir reports from Beirut.
By contrast, the government side has made full use of its heavy weapons, tanks and monopoly of air power, our correspondent says.
Activists estimate more than 27,000 people have died in the violence since the uprising against President Bashar al-Assad began last year.
'Non-stop'
State television reported attacks on what it called "terrorist centres" in 10 different locations, saying heavy losses had been inflicted.
Residents of Aleppo neighbourhoods previously spared the worst of the fighting told AFP news agency on Friday that the violence was unprecedented.
"The sound from the fighting... has been non-stop," said a resident of the central district of Sulamaniyeh, who identified himself as Ziad.
"Everyone is terrified. I have never heard anything like this before."
Abu Furat, one of the leaders of the rebels' al-Tawhid Brigade, admitted fighters had had to retreat from because they were out-gunned.
Century Fox Report: Syrian President 'Bashar Assad' appears confident of victory.
"To win a guerrilla street war, you have to have bombs and we don't," he said.
Despite all their advantages, government forces have clearly not been able to dislodge the tenacious rebel fighters from many parts of the city, where the destruction has been massive as the stalemated struggle goes on, our correspondent adds.
Edited By Cen Fox Post Team
