Bus crash on M3 motorway in Hungary kills 12, injures dozens.

A tourist bus operated by a Polish company came off the road on the M3 motorway in Hungary early on Sunday morning, resulting in one of the country's deadliest bus crashes in recent years.

Twelve people were killed and dozens more injured when the 24-tonne bus overturned after coming off the motorway at around 01:00 local time.

Police believe the driver fell asleep at the wheel, leading to the accident. He has been taken into custody as part of an ongoing investigation.

Thirty-five out of the 57 passengers and two drivers onboard have been rescued by firefighters so far, state media reports.

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Emergency services had been attempting to lift the rear axle of the bus to remove the people trapped underneath before cranes arrived to lift the whole vehicle, according to news agency MTI.

Hungary's ambulance service said it had treated one person with life-threatening injuries, nine people with serious injuries and a further 37 people with minor injuries.

The country's Prime Minister Péter Magyar offered his 'sincere condolences' to the families of the victims and wished those injured a speedy recovery.