Al-Mesalma, who was also known as Mohamed al-Hourani, was shot by a sniper while reporting on fighting in the village of Basri al-Hariri in the city of Daraa, Al-Jazeera reported.
Al-Mesalma had been based in Daraa for about a year, where he reported for Al-Jazeera on the ongoing military clashes between the Syrian army and opposition forces, the reports said.
Local opposition group AEN Network, and local media affiliated with the Syrian opposition, posted a video of the attack, which showed al-Mesalma running across a street with members of an Al-Jazeera crew, and then being shot. The journalist was holding his Al-Jazeera TV microphone at the time of his death.