Syrian warplanes and ground forces have bombarded rebel-held neighbourhoods in Homs as part of the military's ongoing campaign against opposition fighters in the heart of the country's third largest city, activists have said.
The army of President Bashar Assad has been on the offensive in recent weeks, reclaiming some of the territory it has lost to the rebels in the past year.
The Britain-based Syrian Observatory for Human Rights said air strikes hit two districts in the centre of the city, a rebel stronghold since the uprising against Assad began in March 2011. It said the army also fired mortar shells into the neighbourhoods.
An activist from one of those neighbourhoods, Khaldiya, said tanks were also involved in the bombardment, and that the military was trying to push into the area from all sides.
Shelling has been continuous since 10am local time in that area and in nearby Old Homs, activist Tariq Bardakhan told the Associated Press via Skype.
"Today is one of the most violent days that Homs has witnessed since the beginning of the revolution," he said.
In an activists' video of the bombardment, several large explosions can be heard as plumes of grey smoke rise from buildings in a densely built-up area of the city.
The narrator of the video says: "These are heavy explosions that hit Homs, God is great." Another shell lands and smoke can be seen rising from behind a mosque. Two minarets are seen in the distance and the narrator says they belong to the historic Khalid Ibn al-Walid mosque in Khaldiya. The video was posted on the internet and appears consistent with AP's reporting from the area.
The Observatory confirmed fighting around the mosque, and said that part of the building, which dates back to the 13th century and has been damaged in previous fighting, was engulfed in flames. The Observatory said there have been casualties on both sides, but did not have numbers.
Syrian state TV said the army had had "great success" in the battle for Homs after "killing many terrorists in the Khaldiya district". Syrian state media refers to rebels fighting to oust Assad from power as "terrorists" and says they are mercenaries of the West and their Gulf Arab allies who are conspiring against Damascus.