Liberia election: Vehicle rams crowd celebrating President-elect Boakai's victory

At least three people have died and 28 others are in hospital in Liberia's capital after a vehicle rammed into supporters of President-elect Joseph Boakai, a medical officer has said.

The police described the incident as an "accident", but Mr Boakai's party called it an "act of terrorism".

It came just hours after Liberia's electoral body declared him the winner of last week's presidential election.

In his concession speech, President George Weah had called for unity.

The election was closely fought, with just over 20,000 votes separating the two candidates in the run-off poll.

Mr Boakai visited the injured at the main hospital in Monrovia, and promised a full-scale investigation into the incident.

Police said the driver of the vehicle has been arrested.

On Monday evening, Mr Boakai's supporters were celebrating the official announcement of Mr Boakai's victory outside the headquarters of his Unity Party (UP) when the vehicle ploughed into the crowd.

"[The vehicle] just picked up with speed and ran into the supporters," UP spokesman Mohammed Ali told the AFP news agency.

The driver reportedly abandoned the vehicle before fleeing. Angry onlookers set the vehicle on fire.

Eyewitnesses told the Liberian Observer newspaper that they initially thought the incident was caused by a brake failure, but the driver's sudden take-off fuelled suspicions of a planned attack.

"We did not hear anything because the music was playing... I don't really know where the car came from. I just found myself on the ground," Bendu Kiadii, one of those injured, told the Reuters news agency in a hospital trauma ward.

In a statement, the police called what happened "an accident incident" and urged UP supporters to "remain calm" while investigations were under way.

Dr Sia Camanor, the chief medical officer at Monrovia's John F. Kennedy Memorial Hospital, said that three people had died of their injuries.

The number being treated at the hospital had risen to 28 after survivors were brought from other medical facilities. Some are in a critical condition, she added.

Dr Camanor appealed to the public to come forward to donate blood, as some of the victims had lost a lot of it.

In an earlier statement, the UP called what happened a "devastating, wicked and barbaric act of domestic terrorism, leading to loss of precious lives".

The incident followed an election that was deemed largely peaceful, save for some isolated violence in four provinces.

The UP said it was cancelling all celebratory gatherings until further notice.