More than 20 people were killed in Homs on Saturday, a doctor said, as fighting raged around a road junction on a supply line to government forces.
The opposition accuses shabbiha militia loyal to President Bashar al-Assad of killing about 200 Sunni Muslim civilians in Homs in massacres over the last two weeks, but a Syrian ban on most independent media makes such reports difficult to verify.
In a video statement from a makeshift hospital in the city, Mohammad Mohammad, a doctor who has been treating the wounded underground for months, displayed the bodies of five people whose remains had been charred to unrecognisable bits.
"They are the Uzam family. The father, mother and three children—the shabbiha burnt them completely, as part of the annihilation the regime is bringing on the area of Jobar-Kfar Aaya," Mohammad said, referring to districts of Homs.
"We are here surrounded. We have more than 20 dead today. They have been documented by name." He said the victims had died in fighting, bombardment and summary executions.
At least 60 000 people have been killed in Syria's civil war. Mostly Sunni Homs, a commercial and agricultural hub 140km north of Damascus, has been at the heart of the 22-month uprising against Assad.
Syrian authorities have not commented on the latest fighting in the city. In the past, official media have described army operations as designed to "cleanse" Homs from what they described as terrorists.
Speaking from Istanbul after visiting Homs, Mohammad Mroueh, a member of the Higher Leadership Council of the Syrian Revolution, told Reuters: "The rebels are holding their ground but the shabbiha are getting to the civilians.
"It's hard to describe what's happening in terms other than ethnic cleansing of Sunni districts in the way of Alawite supply lines," said Mroueh, who was in Homs earlier this week.
The Alawites, who follow an offshoot of Shi'ite Islam and comprise about 10% of the population, have dominated Syria's power structure and its security apparatus since the 1960s. Assad and most of the ruling elite are Alawites.
A highway that passes near Homs has been used to supply Alawite forces deployed on hilltops in Damascus from bases in the coastal cities of Tartous and Latakia, which have a sizeable Alawite population, according to opposition sources.
Sunnis fear that the city could become part of an Alawite enclave stretching to the coast, where major military bases are located, if Assad was forced to leave Damascus.
"The massacres are increasing and Bashar al-Assad has began to draw borders of this mini-state and associate the Alawites more with blood so that they have no other option but to join him," wrote opposition campaigner Fawaz Tello in an article published on All4Syria news website.
Syria's conflict has grown more sectarian, deepening the Sunni-Shi'ite divide in the Middle East which burst into the open when Shi'ites gained political ascendancy in Iraq following the 2003 US led invasion that deposed Sunni dictator Saddam Hussein.
A statement by an insurgent group, the Syrian Revolution against Bashar al-Assad, said neighbourhoods of southern and western Homs were being hit with battlefield artillery and barrages from rocket launchers.
Activists in Homs said at least 120 civilians and 40 opposition fighters had been killed in the past week and that rebels from the nearby town of Qusair on the border with Lebanon were trying to relieve pressure on the western neighbourhoods.
The armed opposition has been weakened in the city after a drop in ammunition supplies in recent weeks and after Assad's forces tightened a siege on western areas, according to opposition sources.
A counter-offensive by rebels two days ago in the western sector pushed back Assad's forces slightly, but they continued to pound the area with artillery and from the air, the sources said. - Reuters