KIEV • A military plane crash in Ukraine killed 26 people, a tragedy which President Volodymyr Zelensky said would be investigated promptly and impartially.

The transport plane carrying air force cadets on Friday crashed and burst into flames near a highway in the country's north-east.

The State Emergency Service of Ukraine said 27 people had been on board the plane - seven crew members and 20 students. Only one cadet managed to survive.

"Yesterday, as a result of a terrible tragedy... Ukraine lost 26 of its worthy sons," Mr Zelensky said in a post on Facebook yesterday.

"I insist that the causes of this plane crash be promptly clarified and that the investigation be objective and impartial."

He also declared yesterday a day of mourning.

The Antonov An-26 aircraft crashed while trying to land during a training exercise, Ukraine's Defence Ministry said, adding that the black boxes with flight data had been found.

The Ukrainian authorities said they were investigating four possible causes of the crash - a technical malfunction involving the aircraft; improper performance by the crew; improper performance by flight control; and inadequate maintenance.

The State Security Service, a law enforcement agency, said the twin-engine plane crashed five minutes after the crew commander asked to land, following the failure of the left engine.

The crash happened around 2km from a military airport. The cadets were from the Kharkiv University of the Air Force, which is run by the defence ministry. The government said training flights on similar types of aircraft have been suspended.

Many Ukrainians mourned the victims of the tragedy on social media. The US embassy in Ukraine wrote on Facebook: "We send our heartfelt condolences to the families and loved ones of the cadets, officers, and crew killed and injured in the An-26 plane crash."

REUTERS, AGENCE FRANCE-PRESSE