WATCH: Syria Rebels Release Video Showing Kidnapped 'Iranian Mercenaries'

Iranian media reports attack on bus filled with pilgrims in Syria; Free Syrian Army takes responsibility for attack, says those taken included IRG officers.

Syrian rebels have released a video showing who they said were Iranian mercenaries and Revolutionary Guard officials that were kidnapped by opposition forces on Saturday.

On Saturday, Iranian state news agency IRNA quoted an unnamed official in Iran's embassy in Damascus as saying that 48 pilgrims were seized by "armed groups" on the Damascus airport road as they returned from a religious shrine.

Later in the day, however, Iran's semi-official Fars news agency cited a Syrian official as saying that the attack was conducted by soldiers from the Free Syrian Army (FSA), the main armed opposition group working to depose Syrian President Bashar Assad.

On Sunday, the FSA released a video allegedly displaying those kidnapped, taking responsibility for the operation.

However, FSA officials speaking in the video denied Iranian claims that those taken were pilgrims, saying that they were in fact mercenaries who had patrolled the area, and who included offers in the Iranian Revolutionary Guard.

The Syria rebels also said that they would not negotiate the return of the Iranian captives until Iran admits its involvement in the Syrian crisis and pledges to halt aid to Assad's regime.