Iranian Foreign Ministry Spokesman Bahram Qassemi sent a message of condolence over shocking and deadly collapse of the Plasco high-rise in Tehran.
The tragic event claimed lives of 20 fire fighters and wounded 84 others, 5 are still in hospital.
Iran's oldest high-rise in downtown Tehran collapsed on Thursday morning following a major fire in the building, leaving many firefighters buried under rubble.
"The painful and tragic fire incident, collapse of historical building of Plasco as well as financial and human loss of the horrifying incident have caused deep sorrow,” he said in a message.
He also expressed condolences to families of fire fighters trapped in the fire and under debris during rescue operations and lost their lives.
At least 20 firefighters have died after the major commercial building in Iran's capital, Tehran, collapsed following a huge fire, according to the city's mayor.
The confirmation of the death toll by Iranian politician Mohammad Baqer Qalibaf came after conflicting casualty reports earlier on Thursday.
Firefighters battled the blaze for several hours before the building, just north of the capital's sprawling bazaar, fell. Police tried to keep out shopkeepers and others wanting to rush back in to collect their valuables.