The whereabouts of the president are the subject of speculation, with suggestions he may have fled the country. His office has denied all such reports, saying Assad is still at work in Damascus – but there has been no sign of him.
Reports that rebels have seized control of Homs come just over a week since they launched their lightning offensive – the biggest against the Syrian government in years, which has exposed the weakness of the country’s military.
The government has also lost control of the northern cities of Hama and Aleppo, and armed groups in the south say they have taken control of Deraa and Suweida, close to the border with Jordan.
More than 800 people are estimated to have been killed in the fighting, according to the SOHR.
According to the UN, at least 370,000 people have been displaced so far – with many, including Alawites, fleeing the rebels’ approach.
The UN said the fighting was also “worsening an already horrific situation for civilians in the north of the country”.
The UN’s special envoy for Syria, Geir Pederson, on Saturday told the BBC he believed a negotiated way out of Syria’s escalating crisis was still possible, but he also warned it could also go terribly wrong once more in Syria.
Pederson said that various countries were in contact with the rebels and had stressed the need to avoid chaos and bloodshed.
He spoke after attending a meeting in Qatar with representatives of five Arab countries, as well as Iran, Turkey and Russia – the three major outside powers involved in Syria.
In a joint statement, the group said the current crisis posed a threat to regional and international security.