Disturbing footage has emerged online of the moment a bus careened off a road and onto steps leading into an underground passageway in Moscow, killing at least four people and leaving 13 others injured.

The apparent accident happened at around 3am Australian time on Tuesday near Moscow’s Slavyansky Boulevard metro station, near one of the capital’s main avenues.

Moscow police said passengers and pedestrians were among those killed in the crash.

Police immediately ruled out a possibility of it being an attack, saying that they suspect a mechanical fault or that the driver lost control of the vehicle. Police were questioning the driver.

WARNING: Graphic footage

https://twitter.com/BasedMonitored/status/945283761045897216

Moscow police said they were investigating the incident as either a case of the driver losing control or a technical fault.

“The driver of the bus began movement and then changed his trajectory, which resulted in the bus going down into the pedestrian underpass,” police said in a statement.

“The driver has been detained. Police employees are working with him.”

Russian officials inspect the scene after a bus plowed into the subway entrance. Photo: Getty

Footage taken at the scene showed the bus plough through pedestrians walking up the steps leading to the underground passageway.

Russian news agencies reporting from the scene quoted Moscow Mayor Sergei Sobyanin as saying that he has ordered all city buses to be checked in the aftermath of the crash.

The underpass and surrounding area have been cordoned off and several black body bags were photographed on the pavement.

– with agencies