Outbreaks of sporadic but intense fighting between government forces and rebel fighters were reported throughout Syria on Friday, after a double-bombing in Aleppo killed 28 people.
But in the north-west town of Idlib, opposition fighters made a show of strength on the streets, parading in camouflage gear with rifles held in open defiance of the regime.
Crowds cheered as the mainly unmasked fighters marched in a clear demonstration than they were in control of the town.
In the beleaguered city of Homs, however, the Local Coordination Committees (LCC) said that "huge explosions" were heard, followed by "intense gunfire".
Video reportedly shot on Friday showed tanks firing shells towards the city.
Live web broadcasts from residents in Homs throughout Friday showed a subdued city interspersed with sounds of gunfire, falling shells and occasional explosions.
Snipers were reportedly deployed in the streets, and activists said they were targeting "anything that moves".
Security forces were reportedly deployed in the Damascus suburbs, and in Jabal Zawyeh regime forces were said to have carried out 15 arrests and demolished houses using tanks.
It was not possible for the Huffington Post to independently verify many incidents of violence, but several videos uploaded to YouTube and other sites appeared to correspond with the reports.
One video, shot in Dael, Deraa, which is in the south of the country, appeared to show protesters throwing stones at soldiers while being chased by a tank.
Two deadly explosions in the northern city of Aleppo which killed 28 people and injured around 235 were blamed by state media on 'terrorist gangs'.
Broadcasting extremely graphic pictures of human remains in the aftermath of the attacks, Sana News said the blasts highlighted "the reality of events".
The rebel Free Syrian Army (FSA) said it was operating nearby, but denied responsibility for the attacks.
Captain Ammar al-Wawi, told Channel 4 News from Turkey that the regime was trying to "distract" the world from the situation in Homs.
"This explosion has two goals: drawing the attention and pretext for the army to enter Aleppo since the rallies have started there," he said.
Aleppo, which is Syria's largest city, has not previously been the target of sustained violence by either opposition fighters or government forces.
Above: rebel fighters in Idlib making their show of strength.
However activists from the Local Coordination Committee said that demonstrations had taken place in Aleppo on Friday and that six people had been shot.
Videos were also posted on YouTube which appeared to show protests and wounded demonstrators.
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A report released by the Human Rights Watch (HRW) said that makeshift hospitals were "overflowing with the dead".
One resident of Homs told HRW: "I just came from the field hospital. There are three large rooms full of corpses. I’ve seen over 100 corpses today.
"Injured people are dying because we cannot treat them. There are still people in the street who are injured. They are missing body parts. We cannot pull them in because of the shooting. They will die in the street."
Mahmoud, another resident of Baba Amr, said:
"There is no bread, no medication and no nutritional supplies, and after a field hospital was targeted, we lost several of our medical staff."
Describing snipers in Homs picking off wounded civilians, he added: "Many of the wounded have very serious injuries – they lost their limbs, or eyes, had serious wounds to the body. They are in critical condition and are likely to die because there are no medical supplies to treat them properly."
The global protest network Avaaz has launched a $1m appeal for funds to support people in Syria with medical equipment.
Within hours of launching, over $100,000 had been raised, the group said.
Ricken Patel, executive director of Avaaz, said: "Russia and China have given Assad a licence to kill, and the Syrian people are at the darkest part of their night.
Avaaz says it has delivered more than $1.8m of medical equipment already and has smuggled almost two dozen correspondents into the country to report on the situation there.
It was reported by Bloomberg that the political risk monitors Eurasia Group sent a note to clients claiming "civil war" is imminent.
"Recent operations against activists and armed wings of the opposition are proving to be somewhat tactically successful," the note said, according to Bloomberg.
"At the same time, the intensity of clashes indicates that it would be very difficult to fully suppress the uprising. In the next few months, Syria will transition from civil conflict into civil war."
Meanwhile Germany expelled four Syrian diplomats after similar moves by the UK, France, Italy and the United States earlier in the week.
Speaking after meeting the Italian prime minister, Mario Monti, at the White House, American President Barack Obama said:
"We both have a great interest in ending the outrageous bloodshed that we've seen, and see a transition from the current government that has been assaulting its people."
The United Nations says close to 6,000 people have died in the country since the start of anti-government protests in March 2011.