Six people have died and five others were injured after an arsonist set fire to a bus in a small Swiss town.

Police in Kerzers, in the canton of Fribourg, confirmed they had “information that a person was responsible for the fire” that broke out on board the bus at 6.25pm local time on Tuesday.

The cause has not yet been determined, but Swiss outlet Blick reported it had obtained video showing a witness, with his face covered in soot, exclaiming: “A man set himself on fire inside.”

The man, whom Blick said was speaking Albanian, then waved his arms and said: “He poured gasoline and set himself on fire!”

Police have not confirmed the claims, but said in a press conference they had been told a person had doused themselves with petrol on the bus.

A fireman erects a screen around the destroyed bus

A fireman erects a barrier around the destroyed bus – Fabrice Coffrini/AFP

Police declined to comment on the status of the potential perpetrator or if the incident was a terrorist attack.

The public prosecutors’ office in Fribourg will be leading an investigation into the event.

As panicked passengers raced to escape, emergency services found the vehicle “completely consumed by flames” and are still working to extinguish the blaze, police said.

Three of the injured people were taken to hospital in serious condition, at least one of whom was airlifted by helicopter, and the other two were treated at the scene. One of the victims was an emergency services worker, according to Swiss outlet Le Temps.

Police said they do not know how many people were on board the bus and are searching for additional victims.

Investigators examine the charred wreck of the bus

Investigators examine the charred wreck of the bus – KANTONSPOLIZEI FREIBURG/EPA/Shutterstock

The postal bus was travelling from the town of Dudingen and had almost reached its final stop before the fire broke out on the Murtenstrasse in Kerzers, Blick reported.

Car Postal, the bus company, said in a statement: “This tragic news affects us all deeply. Our thoughts are with the injured and the loved ones of the deceased.”

The fire comes months after Switzerland’s deadliest ever blaze which killed 41 people and injured 100 more in the south-east resort of Crans-Montana.

Guy Parmelin, the Swiss president, said: “It distresses and saddens me that once again people in Switzerland have lost their lives in a severe fire. The circumstances are being investigated.

“To the relatives of the deceased from Kerzers, I extend my condolences. And I think of the injured and the rescue workers.”

Police and the fire services at the scene

Police and the fire services at the scene – Laurent Merlet/EPA/Shutterstock

Footage circulating on social media shows flames and smoke billowing out of the burnt out shell of the bus as a person filming can be heard screaming, “oh my god” in German.

The bus is seen sitting on an empty high street, sirens sounding in the background, and firemen rushing to douse the blaze with their water cannons.

They are expected to be at the scene all night, and the road will remain closed until Wednesday morning.

The postal bus was travelling from the town of Dudingen and had almost reached its final stop before the fire broke out on the Murtenstrasse in Kerzers, Blick reported.

The fire comes months after Switzerland’s deadliest ever blaze which killed 41 people and injured 100 more in the south-east resort of Crans-Montana.

Footage circulating on social media shows flames and smoke billowing out of the hollowed shell of the bus as a person filming can be heard screaming, “oh my god” in German.

The bus is seen sitting on an empty high street, sirens sounding in the background, and firemen rushing to douse the blaze with their water cannons.

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