No Armenians were among the casualties after a train smashed into a barrier at Cairo's main train station, the Armenian Embassy in Egypt said in a tweet.

"According to preliminary data, nor Armenian citizens or nationals were among those killed or injured at Cairo’s Ramses train station," the Embassy said.

At least 20 people were killed and 50 injured, as photographs on social media showed clouds of black smoke billowing from the building in central Cairo, Al Jazeera says.

Footage also showed fire engulfing the train and a nearby platform and people rushing to help the injured.

Egypt's National Railway Authority confirmed the accident, saying several people were killed and injured.

In a statement, the authority said the fire broke out after a train derailed and collided with a concrete barrier at the station, without giving further details.

Security sources told the Reuters news agency that there was no indication the crash was deliberate.