KYIV (AFP) - The first Russian soldier on trial in Ukraine for war crimes during Moscow's invasion of Ukraine, pleaded guilty on Wednesday (May 18), facing possible life imprisonment in Kyiv.

Asked in court if he was guilty of the allegations, including war crimes and premeditated murder, 21-year-old sergeant Vadim Shishimarin responded “yes”.

He is accused of killing a 62-year-old civilian in northeast Ukraine in the first days of the Kremlin’s offensive.

Shishimarin – from the Siberian region of Irkutsk – sat in the glass defendant’s box in a Kyiv district court, wearing a blue and grey hoodie.

The youthful-looking soldier with a shaved head looked towards the ground as a prosecutor read out charges against him in Ukrainian.

An interpreter was translating for him into Russian.

He is accused of killing the civilian – allegedly on a bicycle – near the village of Chupakhivka in the eastern Sumy region on February 28.

Prosecutors said Shishimarin was commanding a unit in a tank division when his convoy came under attack.

He and four other soldiers stole a car, and as they were travelling near the village of Shupakhivka in the Sumy region, they encountered a 62-year-old man on a bicycle.

"One of the soldiers ordered the accused to kill the civilian so that he would not denounce them," the prosecutor's office said.

Shishimarin then fired a Kalashnikov assault rifle from the window of the vehicle and "the man died instantly, a few dozen metres from his home", they added in a statement.

The next hearing in the case will take place on Thursday at 0900 GMT.

Prosecutor Andriy Sinyuk told reporters after Wednesday’s hearing that two witnesses – including one of the Russian soldiers who was with Shishimarin at the time of the incident – will be brought to testify in court.

The soldier’s weapon will also be examined as part of the probe, he said.

The Kremlin earlier said it was not informed about the case, saying Moscow’s “ability to provide assistance due to the lack of our diplomatic mission there is also very limited”.

The trial will be rapidly followed by others, with another two Russian soldiers expected to go on trial in central Ukraine on Thursday.

In early May, Ukrainian authorities announced his arrest without giving details, while publishing a video in which Shishimarin said he had come to fight in Ukraine to "support his mother financially".

He explained his actions saying: "I was ordered to shoot, I shot him once. He fell and we continued our journey."

The case is proving challenging, according to his lawyer.

"This is the first such case in Ukraine with such an indictment. There is no relevant legal practice or verdicts on such cases. We will sort it out," he said.

Mr Ovsiannikov said he had not seen any rights violations by the authorities.

Kyiv says it has thousands of ongoing cases and dozens of suspects, vowing to bring them to justice.

The cases will test the Ukrainian justice system at a time when international institutions are conducting their own investigations into abuses allegedly committed by Russian forces.

Ukraine's chief prosecutor Iryna Venediktova underlined the importance of the case for her country in a series of tweets.

"We have over 11,000 ongoing cases of war crimes and already 40 suspects," she said.

"By this first trial, we are sending a clear signal that every perpetrator, every person who ordered or assisted in the commission of crimes in Ukraine shall not avoid responsibility."

Two Russian servicemen are due to go on trial from Thursday for firing rockets at civilian infrastructure in the north-eastern Kharkiv region.