Peace envoy Lakhdar Brahimi heads to Syria on Thursday to meet President Bashar al-Assad, an Arab official said, after admitting he faces an "extremely difficult task" against an escalating conflict.
In violence on Wednesday, rebels killed at least 18 soldiers in a car bomb and ground attack on a military position in Idlib province of northwest Syria, the Syrian Observatory for Human Rights said.
Observatory head Rami Abdel Rahman said "there were 70 to 100 soldiers there when the attack occurred" in the town of Saraqeb.
Separately, four Syrian Armenians were killed and 13 wounded in the war-battered commercial capital Aleppo on the way home from the airport after a trip to Yerevan.
A friend of the victims in Aleppo told AFP: "It's not obvious who opened fire, but the result is that five cars were attacked and four Armenians were killed and 13 or 14 others were wounded."
One of those killed "had left his family behind in Armenia, his wife and kids. He had gone back to take care of some things in Aleppo and then return," the friend said.
Outside Aleppo, fighting erupted at dawn in the Nayrab area, around five kilometres (three miles) from the airport, which remained fully operational, the Observatory said.
Over the past several weeks, rebels have taken to attacking military airfields in an attempt to prevent them from being used for launching air strikes, while commercial facilities have been left unscathed.
Meanwhile, the army shelled a string of neighbourhoods in central Aleppo, including Suleiman al-Halabi, Sheikh Khodr and Qadi Askar, the Britain-based Observatory said.
Helicopter gunships also strafed the rebel district of Bustan al-Basha, a witness said, and the Observatory reported that rebels used rocket-propelled grenades to attack a security branch in the adjacent Midan neighbourhood.
In Hama province of central Syria, the Observatory reported that 20 bodies, including those of two children, had been found in farmland in Halfaya village following an assault by government forces.
In eastern Syria, troops shelled several districts of Deir Ezzor city, and an unspecified number of people were killed in air strikes on the town of Albu Kamal on the border with Iraq, the Observatory said.
Overall, at least 83 people -- 36 soldiers, 34 civilians and 13 rebels -- died in Syria on Wednesday, the Observatory said.
More than 27,000 people have been killed since the revolt against Assad broke out in March 2011, according to figures from the Britain-based monitoring group which gathers its information from a wide network of activists.
-- Brahimi heads for Assad talks --
In Cairo, an Arab League diplomat said Brahimi would head for Damascus on Thursday and meet with Assad the following day, but gave no further details.
Brahimi held talks in the Egyptian capital with Qatari Prime Minister Sheikh Hamad bin Khalifa Al-Thani, briefed envoys to the Arab League and met Syrian opposition officials, UN spokeswoman Vannina Maestracci said in New York.
He told envoys of the Cairo-based League that "he was approaching the crisis in Syria with his eyes open and the full knowledge that it was an extremely difficult task," she told reporters.
The UN-Arab League envoy replaced former United Nations chief Kofi Annan who quit in August over Security Council divisions on the conflict that has gripped Syria for nearly 18 months.
Coupled with the violence is the humanitarian crisis caused by the large number of people fleeing the country or displaced within its borders.
The UN refugee agency said the number of civilians who have fled the violence has reached more than 250,000. And it says more than 1.2 million civilians, more than half of them children, have been displaced inside Syria.
In Beirut, film star and UN special envoy Angelina Jolie said on Wednesday she was moved at how Lebanese families were opening their homes to Syria refugees, after Beirut ruled out setting up camps for them.
"I was very moved today to meet again with the Syrian families. And to meet them here, not in a camp, but in homes where they are welcomed and protected," the Oscar-winning star told reporters.
The Lebanese government has ruled out the possibility of establishing refugee camps amid fears that the crisis in neighbouring Syria could spill across its borders.
Already, areas of northern Lebanon where a large number of refugees have concentrated have come under shelling from inside Syria.
In the embattled city of Aleppo, a rebel commander vowed on Wednesday to retake a major barracks in Syria's commercial capital, a day after it was recaptured by the army.
"We lost the Hanano barracks, and I regret that. But I assure you we will retake it within a week," Abu Mohammed, who did not give his real name, told AFP in a house in the centre of Aleppo.