At least five people have died and 39 others were injured – nine seriously – following a bus crash in southeastern Poland on Friday night.

State news agency PAP said medical rescue services were called to the scene after the Ukrainian bus, carrying 57 people, plunged into a ditch. Initial reports suggested six people had been killed.

"After checking in all hospitals, where the injured were taken, it turned out that there are five casualties," a spokesman for the Podkarpackie region was quoted as saying by the state news agency PAP.

"We know that one person was brought to a hospital in a critical condition. A life-rescuing surgery was conducted and we hope that this life will be saved," the region's governor Ewa Leniart told a news conference.

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The injured were taken to local hospitals and the remaining passengers were brought to a local school. The Kyiv Post reported on Sunday morning that 28 injured remain in hospital.

Pictures from the scene of the crash show a helicopter preparing to airlift the injured to hospitals and the extent of the damage to the bus, which was left mangled by the impact. 

Poland's President Andrzej Duda tweeted a message of condolence after learning of the news on Saturday morning.

He tweeted: "I am deeply saddened by terrible news about the crash of a Ukrainian bus on A4 near Kaszyce in which six people lost their lives and several dozen were injured. My sincerest condolences to the families of the victims and all our Ukrainian friends."

Ukraine's President Volodymyr Zelensky also took to Twitter to thank those who helped to rescue and rush the injured to hospital.

He said: "I sincerely express my condolences to the families of the six victims of a coach accident near Kaszyce. Another 35 of our citizens were hospitalized. Thank you diplomats who did everything possible to help the injured and to establish the causes of the accident."

A spokesman at local medical ambulance services in Przemysl revealed more details about the crash and confirmed the bus was en route to Ukraine.

"The passengers were mostly sleeping when the accident happened, most were not strapped with seat belts, so they were seriously injured. They were mostly young people going home from work," the spokesman said, adding there were no children on board.

He said that the bus hit a traffic barrier while leaving a highway and plunged into the ditch. 

The vehicle was on a 20-hour trip from Poznan in Poland to Kherson in Ukraine when the bus driver lost control, according to a Ukrainian Foreign Ministry statement.

An estimated one million to two million Ukrainians live or work in Poland.