Syrian forces pound rebel-held areas of Homs
Syrian forces have launched a major offensive against rebel-held parts of the city of Homs.
Aircraft, tanks and mortar units attacked several areas, activists say. Unverified footage showed clouds of smoke from explosions across the city.
Syrian state TV said the army had achieved a "great success" in Homs after "killing many terrorists".
The attack follows gains in Homs province by the forces of President Bashar al-Assad in recent weeks.
They captured the strategically important town of Qusair, between Homs and the Lebanese border, in early June.
Rebels say communication lines in Homs were cut on Saturday morning, before the bombardment began.
The city has been a rebel stronghold since the uprising against President Assad began more than two years ago.
An activist in Homs told the Associated Press news agency that the assault was "the worst campaign against the city since the revolution began".
In the Khalidiya and nearby Old City districts of Homs, shelling had been continuous since 10:00 (07:00 GMT), activist Tariq Bardakhan told the agency on Saturday afternoon.
It followed reported shelling in Khalidiya on Friday.
It is hard to be sure how many civilians have stayed in Homs after two years of civil war in which their streets and suburbs have become a battleground, but for those who have stayed this was a desperate day, says the BBC's Kevin Connolly in neighbouring Lebanon.
The UK-based activist group the Syrian Observatory for Human Rights said at least two civilians had been killed, and there had been clashes around the historic Khalid Ibn al-Walid mosque in Khalidiya.
Elsewhere in Syria rebels have claimed some victories, reportedly making gains in fighting in the southern city of Deraa in recent days.
On Friday opposition forces claimed to have captured a major army checkpoint from which it controlled one of the main roads into the city centre.
The UN says more than 90,000 people have been killed in Syria - with a further 1.7m forced to seek shelter in neighbouring countries.