Rebels pressed an offensive in northern Syria on Saturday, attacking Aleppo airport and two airbases, as a rights watchdog and residents reported hundreds of people held in a string of sectarian kidnappings.
Regime troops fended off fierce rebel onslaughts around Aleppo international airport and the adjacent Nayrab military airbase, the Syrian Observatory for Human Rights said.
East of Aleppo, rebel attacks around the Kwiyres military airbase sparked counter-strikes from regime warplanes.
The insurgents launched the "Battle of the airports" on February 12, and have since seized Al-Jarrah military airport and a military complex tasked with securing Aleppo's civilian airport.
Rebels on Saturday also overran a military police checkpoint in the Golan Heights town of Khan Arnabeh just beyond the outer ceasefire line along the demilitarised zone bordering Israel, the Observatory said.
Regime forces responded by shelling Khan Arnabeh and the nearby village of Jubata al-Khashab, inside the ceasefire zone, forcing a rebel retreat.
The Israeli military said it had taken five Syrians wounded in clashes on the Golan to a hospital inside the Jewish state.
An Israeli military spokeswoman said "soldiers provided medical care to five injured Syrians adjacent to the security fence" on the strategic plateau.
The Golan has been tense since the near two-year Syrian uprising morphed into a bloody insurgency, at times spilling over with mortar and gunfire into the Israeli-held zone but with serious escalation so far contained.
Northwestern Syria has meanwhile fallen into a security vacuum, illustrated by reports on Saturday that more than 300 people were abducted in tit-for-tat kidnappings in 48 hours, the Britain-based Observatory and residents said.
The spate of abductions, involving large numbers of women and children, began on Thursday when upwards of 40 civilians from majority-Shiite villages were kidnapped by armed groups in Idlib province.
Hours later, more than 70 people from Sunni areas were seized in retaliation by gunmen from nearby Shiite villages. Subsequently, dozens more people from mostly Sunni opposition towns were captured.
Most of the rebels fighting the Damascus regime are Sunni, while the ruling clan and many of its most fervent supporters are members of the minority Alawite sect, an offshoot of Shiite Islam.
Kidnappings driven by a hunger for ransom but often tinged with sectarianism have multiplied in Syria during the revolt that the United Nations says has killed more than 70,000 people.
On the diplomatic front, French Foreign Minister Jean-Yves Le Drian at a security forum in Abu Dhabi called for urgent action to bring about a power transfer that excludes Syria's President Bashar al-Assad.
Le Drian said the change should be "a transition in which President Assad would no longer keep his place," and accused Assad and his family "of clinging to power by multiplying the daily massacres and atrocities."
His remarks came after the umbrella opposition National Council on Friday refused to accept Assad in any talks on ending the 23-month conflict, as part of a "framework" it has drawn up for a political solution.
The council singled out the regime's most powerful backers, Russia and Iran, calling on the former to ensure there are "adequate safeguards" to make the peace process possible, together with the United States.
It also urged Iran to recognise that Tehran's support for Assad "is pushing the region towards sectarian conflict."
The leader of the Shiite militant group Hezbollah, meanwhile, said on Saturday that while Syria may be weakened by its bloody conflict and unable to fight against Israel, his organisation was capable of defending Lebanon.
"Those who think Syria is no longer a player and cannot help the resistance (Hezbollah)... and that the resistance is going through a period of weakness and confusion are mistaken," key Damascus ally Hassan Nasrallah told a Beirut crowd.
"We have everything we need in Lebanon. We don't need to transport (arms) from Syria or Iran."