Five people were killed when a city bus ploughed into a pedestrian underpass in western Moscow on Monday, traffic police said.
It was not immediately clear what caused the accident as authorities said they were looking into several possibilities, including a technical malfunction.
"A bus drove into a pedestrian underpass," a traffic police spokesman, Artyom Kolesnikov, told AFP.
"According to preliminary information, five people died."
Footage broadcast on national television showed a bus driving onto the pavement and then down the stairs of the underpass, running over several pedestrians before coming to a stop.
Moscow police said in a statement they were looking into two possible causes of the accident -- the driver losing control of the vehicle and a technical problem with the bus.
"The driver of the bus began movement and then changed his trajectory, which resulted in the bus going down into the pedestrian underpass," the statement said.
"The driver has been detained. Police employees are working with him," the statement said.
Three people have been hospitalised, the statement added.
The accident happened around 3 pm (1200 GMT) near Moscow's Slavyansky Boulevard metro station, a prestigious residential area near one of the capital's main avenues.
Sirens were blaring around the metro station, with authorities preparing to pull the bus out of the underpass with a cable, an AFP correspondent at the scene said.
The underpass and surrounding area were cordoned off by police, and several black body bags could be seen on the pavement, partially covered with falling snow.
The emergencies ministry said two helicopters had been dispatched to the scene to help evacuate the victims.
"There are dead and wounded," tweeted Moscow mayor Sergei Sobyanin. "We are providing emergency aid," he said, offering condolences to families of the victims.
Sobyanin himself arrived at the scene, telling journalists he had ordered a full inspection of the entire Moscow bus fleet.
