Ukraine has started its first war crimes trial since the beginning of Russia's invasion, with a 21-year-old soldier appearing in the dock accused of killing an unarmed civilian.

It is accused that Shishimarin fired an automatic rifle from a car window and killed an unarmed 62-year-old civilian. This was allegedly done to ensure that there was no witness to the carjacking.

He was ordered to shoot the civilian to stop them from telling Ukrainian defenders about their location, according to the prosecutors.

It is not clear how he was captured or what the nature of the evidence against him is.

He faces possible life imprisonment on charges of war crimes and premeditated murder.

Russia has denied targeting civilians and made no comment on the trial.