Syrian forces clashed with rebels around Aleppo's television and radio station on Saturday August 4, activists said, and a local rebel commander said his fighters were preparing for a "strong offensive" by government forces on the country's largest city, Reuters said.

Syrian troops back by armor stormed the last opposition bastion in Damascus on Friday in a drive to crush a rebel offensive that coincided with a bomb attack that killed four of President Bashar al-Assad's top security officials.

Syria's civil war has intensified in the last few weeks, with fighting engulfing Damascus and Aleppo for the first time in the 17-month-old uprising against Assad family rule.

The two cities are crucial prizes for both sides in an increasingly brutal struggle that has eluded all attempts at a diplomatic solution and risks igniting a wider conflagration.

The Syrian Observatory for Human Rights, which said 110 people had been killed on Friday, including 88 civilians, also confirmed the clash near the television and radio station. It said the terrestrial signal for Syrian television in Aleppo had been cut off.

Syrian television said a large number of terrorists, the term it uses for the rebels, were killed and wounded after they tried to storm the television and radio station in Aleppo.

In Aleppo, a Syrian activist told Reuters the rebels had sought to extend their area of control from the Salaheddine district, where the most intense fighting has been focused, northwards to the area around the television and radio station.

"The Free Syria Army pushed from Salaheddine to al-Adhamiya where they clashed this morning with Syrian troops. But they had to retreat," activist Barraa al-Halabi told Reuters.