Fighting has spilled over to a town near the Turkish border with Syria as rebels from the Free Syrian Army continue to clash with the government's forces.
The Syrian Observatory for Human Rights (SOHR), a Britain-based organisation, said members of the FSA clashed with government troops in the town of Azaz in the northern province of Aleppo.
At least three soldiers died, said SOHR.
It said military helicopters were seen flying over the town, which is just 8km (5 miles) from the Turkish border.
"Troops are bombing and helicopters flying overhead. Fighting has been going on since midday [Thursday] between regime forces and deserters in Azaz," opposition activist Mohammed Halabi told AFP.
The online edition of Al Arabiya said opposition sources had told its correspondent that two government soldiers were killed and 18 captured.
FSA fighters said they had captured large quantities of ammunition after they attacked a government unit near the village of Bedama, also near the Turkish border, the report added.
On 22 March, Syrian forces attacked a bus on its way to Turkey. Passengers included women and children. The attack took place in Semin, a town in Idlib, a northwestern province also near the border. At least 10 people were killed, SOHR said.
Reprisals against the year-long uprising to bring down the regime of President Bashar al-Assad continue to be savage, it added. More than 100 activists detained in a prison in Idlib province were tortured to death and shelling has continued in the districts of Bab Dreib, Safsafa and Warsheh in Homs.
In a single day, at least 70 people died across the country.
In a bid to step up pressure against the government of Assad, the UN Human Rights Council condemned the violence and extended the mandate of a UN panel of experts tasked with reporting human rights violations in Syria.
The resolution condemned "widespread, systematic and gross violations of human rights and fundamental freedoms perpetrated by the Syrian authorities".
It also condemned "the deliberate destruction of hospitals and clinics, the obstruction and denial of medical assistance to the injured and sick, and the raids and killing of wounded protesters in both public and private hospitals".
UN-Arab League peace envoy Kofi Annan was visiting Moscow and Beijing to discuss his proposals to halt violence.
The plan calls for a ceasefire first by the Syrian government and a daily two-hour halt to fighting to facilitate humanitarian work and "inclusive Syrian-led political talks" but opposition group have criticised the initiative as it does not call for Assad to step down.
The EU has also imposed sanctions on four members of the Assad family, including his wife Asma al-Assad, and eight government ministers.
The UN estimates that more than 8,000 people have been killed since the uprising began in March 2011 but activists and Syrian rights group say up to 9,100 have died.