A warplane has been shot down and the pilot captured by rebels in an area south of the Syrian city of Aleppo where insurgents are battling the Syrian army backed by allied militias, the Syrian Observatory for Human Rights said.
State TV said the warplane was shot down with a surface-to-air missile while on a reconnaissance mission over the northern province of Aleppo, adding that the pilot ejected and "work is ongoing to rescue him."
Opposition activists said the warplane was shot down near the village of al-Ais that was captured Saturday by insurgents spearheaded by members of the Nusra Front - al-Qaeda's branch in Syria.
Ahrar al-Sham, a hardline Islamist group that fights alongside Al-Qaeda's local affiliate, said it "shot down a warplane (over the town of Al-Eis) that was conducting airstrikes".
Earlier, a rebel source had confirmed that a regime warplane had been shot down, but said it was likely by fighters from Al-Qaeda's Syrian branch, Al-Nusra Front.
The insurgents also shelled a predominantly Kurdish neighbourhood in the city of Aleppo, killing at least nine people.
The downing of the warplane and latest fighting and shelling in Aleppo, Syria's largest city and former commercial centre, threaten to undermine a US-Russia-brokered ceasefire that has largely held since February 27.
The Britain-based Syrian Observatory for Human Rights said the pilot was captured by Nusra Front members, who took him to one of their offices in the area. The Local Coordination Committees said the warplane was a Sukhoi 22.
An amateur video posted online showed a man who appeared to be a pilot as he was being captured by militants in the area.
"Shame on you, you filthy pig," some of the fighters said as they surrounded the man. A fighter could be also heard shouting "take away his gun." The video appeared genuine and corresponded to other AP reporting of the events In Moscow, Defense Ministry spokesman Major General Igor Konashenkov said no Russian warplanes flew over Aleppo on Tuesday.
Syrian rebels have shot down several Syrian warplanes since the country's crisis began in March 2011. Russian warplanes have been carrying out air strikes in Syria since September 30. Syrian militants have not downed any Russian planes. Neighbouring Turkey, however, shot down one Russian aircraft last year.
Also Tuesday, the U.N. special envoy for Syria will head to Moscow ahead of the planned resumption of indirect peace talks between the Russia-backed government of Syrian President Bashar Assad and opposition groups next week in Geneva.
Staffan de Mistura's office said he was to meet on Tuesday with Russian Foreign Minister Sergey Lavrov to discuss the next round of the talks.
The so-called "proximity talks" between Assad's envoys and representatives of the opposition adjourned last month, after nearly two weeks during which de Mistura shuttled between the delegations.
The talks achieved no significant breakthroughs. U.N.-designated terror groups such as the Islamic State group and the Nusra Front, are not involved in the talks or the ceasefire.
Earlier in the day, activists said insurgents, including Nusra Front members, shelled the predominantly Kurdish Sheikh Maqsoud neighbourhood in Aleppo.
The Observatory said the shelling came amid clashes between militants and Kurdish fighters. The activist group says nine were killed.
The state SANA news agency said the rocket attack on Sheik Maqssoud killed 15 and wounded about 100.
Sheik Maqsoud is on the northern edge of Aleppo and has been repeatedly targeted by militants over the past few months amid fighting on its outskirts.
On Monday, state media reported that insurgents fired dozens of shells at the same neighbourhood, killing eight and wounding more than 20.