Syrian state media say a pilot ejected Monday after suffering technical problems, while rebels claimed they shot down the government's warplane.
The official news agency
SANA said a military plane encountered technical problems during what it called a "routine training mission" in eastern Syria. The pilot ejected and authorities are now searching for him.
Opposition activists posted amateur video on YouTube showing a fighter jet flying through the sound of heavy fire, erupting in a ball of flames and trailing a line of smoke. Someone off-camera celebrates, saying the plane had been hit in the town of Mohassen in Deir al-Zor province.
It is not possible to independently verify the video or the observer's claims.
According to eyewitness reports, the Syrian government has been using fighter jets as part of its most recent assaults on rebel-held areas across the country.
In the latest violence, opposition activists say 50 Syrians -- including 31 civilians -- have been confirmed dead so far Monday.
The British-based Syrian Observatory for Human Rights said most of the deaths occurred during a government bombardment on the town of Irbeen. It is impossible to independently verify the claim.
A Free Syrian Army fighter observes the area during clashes in Aleppo, August 16, 2012.
A Free Syrian Army fighter carries the body of a fellow fighter in Aleppo, August 16, 2012.
A Free Syrian Army fighter reads the Quran before clashes in Aleppo, August 16, 2012.
A man searches among houses that were destroyed during a recent Syrian Air Force air strike in Azaz, August 15, 2012.
Syrians evacuate a wounded man from under the rubble after an air strike destroyed at least ten houses in Azaz on the outskirts of Aleppo, Syria, August 15, 2012.
Injured Syrian women arrive at a field hospital after an air strike hit their homes in the town of Azaz on the outskirts of Aleppo, Syria, August 15, 2012.
A Syrian man carries an injured child to a field hospital after an air strike hit homes in Azaz on the outskirts of Aleppo, August 15, 2012.
Wounded Syrians arrive at a field hospital after an air strike hit their homes in Azaz on the outskirts of Aleppo, August 15, 2012.
Syrians wounded in an air strike that hit their homes evacuate a field hospital after a second air strike in Azaz on the outskirts of Aleppo, August 15, 2012.
Wounded Syrians evacuate a field hospital after a second air strike in Azaz on the outskirts of Aleppo, August 15, 2012.
A Free Syrian Army fighter passes an AK-47 rifle to his fellow fighter in Aleppo, August 14, 2012.
A Free Syrian Army fighter reacts after hearing news that his commander had been killed by tank shell in Aleppo, August 14, 2012.
A Free Syrian Army fighter fires his sniper rifle from a house in Aleppo, August 14, 2012.
Free Syrian Army fighters sit behind a barricade on a street in Aleppo, August 13, 2012.
A Free Syrian Army fighter observes the area with a pair of binoculars in Aleppo, August 13, 2012.
Later this week, the United Nations humanitarian chief is expected to travel to Syria and Lebanon to discuss ways of increasing aid to civilians caught up in the conflict.
Valerie Amos announced Monday that the three-day visit, beginning Tuesday, is aimed at drawing attention to the deteriorating humanitarian situation in Syria, and the impact on people who are still in the country and those who have fled to other countries, including Lebanon.
Some information for this report was provided by AP, AFP and Reuters.