Syrian troops have stormed the last rebel stronghold in the capital Damascus, activists say, as the country's largest city, Aleppo, was pounded by artillery and helicopters.
Activists said most of the capital's Tadamon district was under the control of government forces by early Friday evening, after "thousands of soldiers" entered the neighbourhood with tanks and armoured vehicles.
"Thousands of soldiers have entered the neighbourhood, they are conducting house-to-house raids," a resident, who did not want to be identified for security reasons, said by telephone.
The army had been trying to enter Tadamon for more than a week but was pushed back by fierce resistance from the rebels.
The Free Syrian Army launched increasingly bold attacks in the country's two main cities and established strongholds in relatively central neighbourhoods. Government forces responded by shelling the rebellious neighbourhoods, forcing thousands of people to flee.
Police station 'captured'
Al Jazeera's Ahmad Zeidan, reporting from Aleppo, said the Free Syrian Army is gaining ground, despite intensifying attacks from Syrian forces.
"I would say last night has been the heaviest in terms of bombardment faced in Aleppo," he said on Saturday morning, adding there was prominent use of artillery and the use of helicopter gunships.
He also said according to FSA contacts on the ground, they have broken into the television and radio station based in Aleppo.
Syria state TV, however, reported a large number of fatalities from the FSA who were killed while raiding the TV and radion station.
The Syrian army has reinforced its positions in and around Aleppo over the past two weeks, while conducting daily artillery and aerial bombardments of rebel forces in the city.
Fighting in Aleppo has focused on the Salaheddin district, seen as a gateway to the city for the Syrian army, which uses it to send reinforcements.
Fighters told Reuters journalists inside Aleppo on Friday that they had captured a large police station after days of clashes.
In-depth coverage of escalating violence across Syria
Rebel commander Abu Zaher said fighters had taken several police officers prisoner and seized weapons and ammunition.
Other rebels said an estimated 20 civilians had been killed in the neighbourhood. They say 50 of their fighters have been killed there in the last several days.
Rebels said earlier on Friday they had taken control of more than "50 per cent" of Aleppo.
The FSA claimed to have consolidated most of its control in the city's east, while also maintaining a grip on central neighbourhoods including Salaheddin and Bab al-Hadid.
Internet and telephone networks in Aleppo were mostly cut for the third day, hampering attempts by rebels to co-ordinate and forcing them to use couriers to deliver orders. Soldiers were launching rockets at fighters from an infantry school north of Aleppo, Reuters reported.
Areas around the city are divided, with some villages loyal to Assad and others favouring the opposition.
Meanwhile, Ban Ki-moon, the UN chief, said "acts of brutality" reported in Aleppo could be crimes against humanity. His comments came before the UN General Assembly adopted a resolution deploring the Security Council for lack of action.
Both sides have accused each other of carrying out summary executions of prisoners in the city.