DAMASCUS: Rebels pressed the "Battle of the airports" in the north on Sunday, attacking three key facilities as the main opposition bloc accused staunch Damascus ally Hezbollah of "military intervention" in Syria.
The UN rights chief, meanwhile, urged international action against President Bashar al-Assad, even to the extent of weighing military intervention.
On the ground, troops parried fierce rebel attacks near Aleppo airport, the adjacent Nayrab military airbase and Kwiyres airbase east of Aleppo city overnight, the Syrian Observatory for Human Rights said.
The insurgents launched their offensive against airports in the north on February 12, and have since seized Al-Jarrah military airport and Base 80, which was tasked with securing Aleppo's civilian airport.
The Syrian National Council, meanwhile, accused members of Lebanon's powerful armed movement Hezbollah of entering the nearly two-year conflict in Syria.
It said Hezbollah fighters crossed into Homs province on Saturday and attacked "three Syrian villages in the Qusayr region near the Lebanese border."
The operation led not only to "civilian casualties and the exodus of hundreds of people," but has also "stoked sectarian tensions" in the area, the SNC said in a statement.
On Saturday, the Local Coordination Committees -- a grassroots network of activists on the ground in Syria -- had also reported fighting between rebels and Hezbollah members around Qusayr.
It said they were trying to break into the rebel-held city, which has been under daily army bombardment for the past year.
Lebanon's Hezbollah is Shiite, while most of Syria's population and the rebels battling Assad's regime are Sunni. The ruling clan and many of its most fervent supporters belong to the minority Alawite sect, an offshoot of Shiite Islam.
The SNC said Hezbollah was opening using heavy weapons "under the auspices of the Syrian regime army."
This is a "serious threat to Syrian-Lebanese relations and regional peace and security," it said, adding that the Beirut government has a responsibility to end this "aggression."
Lebanon is sharply divided over the uprising in its larger neighbour, with Hezbollah and its allies in the ruling coalition backing Assad's regime and the Sunni-led March 14 movement and its allies supporting the rebellion.
The Observatory, meanwhile, reported that eight foreign fighters in Aleppo were among 36 rebels killed in Syria on Saturday, along with 37 civilians and 31 government troops.
UN rights chief Navi Pillay said the international community was hesitating to take action on Syria, weighing up whether military intervention would be worth it.
Urging that some sort of international action be taken against Assad, Pillay repeated her call for him to be investigated for "crimes against humanity and war crimes."
Asked by Britain's Channel 4 television whether it would be difficult for the United Nations to intervene in a place like Syria, she said: "It's an intergovernmental decision on what kind of action: intervention, peacekeeping, military intervention or a referral to the international criminal courts.
"We urge that action be taken immediately. If there is doubt or hesitation it is because people are assessing the value of military intervention in places like Libya, Syria and Afghanistan.
"It could become a long, drawn-out war with no guarantees that civilians would not be harmed in that process."
The Syrian conflict, which began in March 2011 with unprecedented mass protests and morphed into an armed insurgency after a harsh state crackdown, has left nearly 70,000 people dead, according to the United Nations.