Terrified residents cowered in their homes on Monday in Syria's Homs, as army tanks fired shells, machineguns and mortars into their neighborhoods, and amateur video filmed by anti-government activists showed carnage in a city street.

Four bodies of what appeared to be male civilians lay bloodied under fallen power lines in a narrow alleyway of the Baba Amr district, their limbs twisted, heads gashed and brains spilling out.

"What is happening is a slaughter," said Fadi, a resident near Baba Amr who spoke to Reuters on Skype. "They hit people with mortar fire."