Fighting raged between troops and rebels in Syria as Damascus ratcheted up the tension with Ankara by banning all Turkish passenger flights from Syrian airspace from Sunday.
Rebels and activists said a Syrian regime warplane was shot down near Aleppo, while part of the embattled northern city's historic Ummayad mosque was set ablaze in fighting as rebels attacks army positions inside, monitors said.
And a car bomb blast near Damascus killed eight people, including a child and two women, in Al-Nabak on the road to Homs province, said the Syrian Observatory for Human Rights.
As the fighting on the ground escalated, so too did the tension with Turkey.
Syria banned Turkish passenger flights from midnight (2100 GMT) Saturday, state news agency SANA said, citing the foreign ministry.
The suspension came after Turkey and Syria engaged in sporadic cross-border shelling last week.
The decision, "in accordance with the principle of reciprocity", was in retaliation for Turkey's decision to stop Syrian civil aviation flights over its territory, SANA said.
The Turkish government has not announced a similar ban for Syrian civilian aircraft.
However, Turkish jets forced a Syrian passenger plane en route from Moscow to Damascus to make an emergency landing in Ankara on Wednesday on suspicion it was carrying weapons.
Both Damascus and Moscow denied the claim, and the plane was allowed on Friday to continue on its journey.
Russian Foreign Minister Sergei Lavrov said the Syrian Air passenger plane had been carrying radar equipment that could have either civilian or military uses, and insisted that Moscow had violated no laws.
Turkish Prime Minister Recep Tayyip Erdogan called for reform of the UN Security Council to help resolve the crisis, after Russia and China have repeatedly used their veto powers to block resolutions condemning Syria.
"It's time to change the structure of international institutions, starting with the UN Security Council," Erdogan told reporters, calling for "wider, fairer and more effective representation".
In Istanbul, Erdogan and Foreign Minister Ahmet Davutoglu held talks on Syria with visiting Arab League chief Nabil al-Arabi, Turkish news agency Anatolia said.
With rebels controlling large swathes of the border area, several incidents of cross-border fire from Syria this month sparked retaliatory shelling by NATO member Turkey and raised concern about potential escalation.
After meeting with German Foreign Minister Guido Westerwelle, Davutoglu repeated that Turkey would not tolerate any further border incidents.
"We will hit back without hesitation if we believe Turkey's national security is in danger," he said.
Westerwelle reiterated Germany's support for its NATO ally Turkey while at the same time appealing for restraint.
"We are on Turkey's side but we also call on Turkey to show moderation," he said.
Peace envoy Lakhdar Brahimi, a veteran Algerian diplomat who is the envoy of the United Nations and the Arab League, arrived in Istanbul from talks in Saudi Arabia.
He is due in Tehran on Sunday for talks with Foreign Minister Ali Akbar Salehi, Iranian state television channel's website reported, a day before heading for Baghdad to meet Iraqi Prime Minister Nuri al-Maliki.
The envoy is on a regional tour aimed at finding a solution to the conflict in Syria after Damascus rejected a UN call to implement a unilateral ceasefire.
On the ground, rebels blocked army reinforcements from advancing towards the town of Maaret al-Numan, which has been under rebel control for several days, an AFP journalist in the area said.
In its bid to retake the town, strategically located in the northwest on the road from Damascus to the embattled city of Aleppo, warplanes bombarded it, killing two civilians and destroying three homes.
The rebel Free Syrian Army seized Maaret al-Numan on Tuesday, pushing the army out to two military bases on its outskirts and blocking the arrival of reinforcements to Aleppo.
At least 12 rebels were killed late on Friday in air strikes south of the town, where fierce battles were taking place, the Syrian Observatory for Human Rights said.
In Aleppo itself, fierce clashes raged in and around the Umayyad mosque, an AFP journalist said. Rebels entered into the complex by planting an explosive device at the southern entrance, a military source said.
Rebels say the army used the massive mosque complex as a base of operations because of its strategic location.
"The fighting caused a fire to break out in part of the complex," said Syrian Observatory director Rami Abdel Rahman.
Elsewhere, rebels seized a base in Deir Foul village near the rebel-held town of Rastan in Homs, said the Observatory, and another base in Atibah in Damascus province.
The Britain-based monitoring group said at least 101 people were killed on Saturday -- 36 civilians, 33 soldiers and 32 rebels.
More than 33,000 people have now been killed since the uprising against Assad's rule erupted in March last year, it added. Hundreds of thousands more have fled their homes.
The UN estimates that more than 2.5 million people have been affected by the fighting. There are more than 348,000 Syrian refugees registered in neighbouring countries, but many more are unregistered.