Hezbollah leader Sayyed Hassan Nasrallah on Monday denied the Lebanese group had received chemical weapons from Syria.
Members of the Istanbul-based opposition Syrian National Coalition had accused Syrian President Bashar al-Assad's government of transferring chemical weapons to Hezbollah to escape inspection.
"This accusation is truly laughable," Nasrallah said in a televised speech. "We understand the dimensions and background of these accusations, and these have dangerous consequences for Lebanon.
"We decisively and conclusively deny these accusations which have absolutely no basis in truth."
Hezbollah has backed Assad in the conflict in neighbouring Syria and has sent troops across the border to fight on the government's side.
Syria has agreed to give up its chemical weapons under a plan agreed by the United States and Russia after Western powers accused Assad's government of carrying out a chemical attack that killed hundreds of people in a Damascus suburb last month.