Ankara and Tehran: At least 20 firefighters were killed when a 17-storey Tehran commercial building collapsed on top of them as they tried to put out a blaze, Iranian state television quoted the city's mayor as saying on Thursday.

But there was confusion over the toll, as a fire department spokesman said soon afterwards that there was still a chance of finding them alive.

Soldiers, sniffer dogs and rescue workers were searching the ruins of the Plasco building after it crashed down in a giant cloud of dust. The collapse was shown live on state television. One witness described it as "like a horror movie".

"At least 20 firefighters who were trapped under rubble have died," Mayor Mohammad Baqer Qalibaf said. "They are martyrs. They lost their lives when trying to help people."