The denial was issued by Hezbollah sources cited by Russia Today's Arabic service, who claimed false rumours had been spread via social media.
The sources were quoted as claiming Hezbollah leader Hassan NasraIlah would also deny the reports in a speech due to be given later on Wednesday.
The reports that Qassem was seriously wounded in the roadside boming of a convoy with senior government officials aboard, were said to have been spread by Free Syrian Army rebels via Facebook and Twitter.
The convoy was allegedly blown to pieces in the attack which occurred on a highway in the town of Jdeidet Yabous, near the border with Lebanon, according to the reports.
An alleged rebel leader nicknamed Abu Maher also confirmed the report on Arabic satellite TV channel al-Arabiya.
Also on Wednesday, mortars were fired close to the Literature Faculty of Damascus University, state TV reported without providing further details.