A military transport plane carrying air force cadets crashed and burst into flames near a highway in northeastern Ukraine.
Searchers combing the area where a Ukrainian military aircraft crashed have found two more bodies, bringing the death toll to 26. One person survived.
Ukrainian President Volodymyr Zelenskiy said on Saturday the causes of a military plane crash which killed 26 people would be investigated promptly and impartially.
A military transport plane carrying air force cadets crashed and burst into flames near a highway in northeastern Ukraine on Friday evening.
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," Zelenskiy said on Facebook. "I insist that the causes of this plane crash be promptly clarified and that the investigation be objective and impartial."
"Twenty five died on the spot," he said, adding one more cadet died in hospital from extensive burns.
"It is difficult to find words to express the pain of this loss."
Zelensky arrived at the scene of the tragedy near the eastern city of Kharkiv where the plane burst into flames on landing around two kilometres (more than one mile) from Chuguiv military air base. Firefighters extinguished the blaze after an hour.
He declared Saturday a day of mourning.
Four possible causes of the crash
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.
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 Ukrainian law enforcement agency, said the plane crashed five minutes after the crew commander asked to land after the left engine of the twin-engined plane failed.
"According to the preliminary information, the cadets did not directly control the aircraft - all flights were performed by the crew commander," the State Security Service said in a statement on Saturday.
The crash happened around 2 km (1.2 miles) from a military airport.
The cadets were from the Kharkiv University of the Air Force, which is run by the defence ministry.
43 years old plane
Zelenskiy ordered that flights of An-26 planes be halted pending investigation of the crash cause.
Defence Minister Andriy Taran said "the plane likely caught the ground with its wing" and then caught fire.
"Everything went according to plan: the plane was performing a training flight for cadets," he was quoted as saying by the defence ministry.
He said the instructor was at the wheel and cadets took turns to sit next to the pilot.
The An-26 is a transport plane used by both military and civilian operators. Nearly 1,400 of the planes were manufactured from 1969 to 1986, according to the company's website.
Taran said the plane was made in 1977 but was in a good condition.
Just learned about the tragic military plane crash this evening in Chuhuiv, Ukraine. My thoughts are with the families and friends of those who lost their lives. My condolences on behalf of the EU to President @ZelenskyyUa, Minister @DmytroKuleba and @DefenceU Minister Taran— Josep Borrell Fontelles (@JosepBorrellF) September 25, 2020
A number of foreign leaders including Turkish Foreign Minister Mevlut Cavusoglu, Polish President Andrzej Duda, Canadian Prime Minister Justin Trudeau and the EU's top diplomat Josep Borrell expressed their condolences.
"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," the US embassy in Ukraine said on Facebook.
Terrible tragedy for the whole Ukraine. A military plane crashed in the Kharkiv region, at least 20 people have died. Our hearts and thoughts are with the families of the victims. We are grieving together with them. pic.twitter.com/s7btFRqlGk— Ukraine's Mission to the EU (@UA_EUMission) September 25, 2020