At least two people have been killed and seven injured after a bus exploded in central Yerevan, Armenia’s capital, according to the national emergencies ministry.

The emergency services were informed of the blast at approximately 10:00pm local time, the deputy head of the rescue service of the Ministry of Emergency Situations, Major-General Nikolay Grigoryan, told journalists, TASS reported.

“Though at first it was thought that one person got killed in the blast, fragments of the second body were found later during observation of the bus and the site,” Grigoryan said. Both bodies are unidentified.

All injured in the blast are Armenian citizens, TASS reported citing the country’s emergencies ministry. The injured have been taken to a nearby 'Armenia' medical center, Grigoryan added.

Grigoryan also denied earlier reports that the bus driver had been killed, saying that the man managed to escape injuries and had been questioned by the police.

Commenting on the cause of the incident he said that the “investigation is yet to determine it”.

The explosion hit a No.63 bus on Alabyan Street in the Armenian capital.

“The reason for the explosion haven’t been established yet. The experts are working on site,” Ashot Agaronyan said, as cited by RIA Novosti.

The Emergencies Ministry has ruled out a gas explosion as the possible cause of the blast as the bus had been running on diesel fuel. According to eyewitness accounts, the blast was heard at remote distances in a neighboring city area, Sputnik reported.

Although the cause of the blast remains unclear, police have not ruled out the possibility of a bomb attack.

“An explosive device could have been set off in the bus in Yerevan,” Vladimir Gasparyan, Armenia’s police chief said. However, he said that the cause of the blast will only be clear in the next few hours and it is too early to give a concrete conclusion. Police also stressed that all theories are preliminary and Armenia’s Investigative Committee said they will not comment on the situation until an investigation has been carried out.