Syrian state television said soldiers found chemical agents in rebel tunnels in the Damascus suburb of Jobar on Saturday and said some soldiers were suffocating.
"Army heroes are entering the tunnels of the terrorists and saw chemical agents," state television quoted a "news source" as saying. "In some cases, soldiers are suffocating while entering Jobar," it said.
"Ambulances came to rescue the people who were suffocating in Jobar," it said, adding that an army unit was preparing to storm the suburb in which rebels fighting to oust President Bashar Assad are based.
Syrian activists accuse Assad's forces of launching a nerve gas attack in Jobar and other suburbs before dawn on Wednesday, killing hundreds.