"A passenger bus Ikarus was caught on fire at 4:30 a.m. GMT on the road, connecting Russia's city of Samara and Kazakh city of Shymkent," Imankulov said.
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There were 55 passengers and two drivers in the bus, the official said, adding that the passenger's citizenship was being defined.
"Five passengers, who managed to escape, are undergoing medical treatment, while other 52, including two drivers, died," Imankulov added.
The Kazakh authorities have deployed the police, the emergency service, medical workers and psychologists at the scene of the incident.