The victims were serving in a brigade of marines and their bodies were found in the house where they were living temporarily, an Ukrainian military statement said.

The shootings took place near the village of Shyrokyne around 10 kilometres (6 miles) from the strategic government-held city of Mariupol, the Prosecutor-General's spokeswoman Larysa Sargan said on Facebook.

She said that two marines had been detained on suspicion of murder after allegedly "confessing to the circumstances of the murder perpetrated on the basis of hazing while serving in the military."

More than 2,750 Ukrainian servicemen have been killed in fighting between the government forces and Russia-backed rebels in eastern Ukraine since the conflict broke out in April 2014, President Petro Poroshenko has said.

Ukrainian media estimates claim that Kiev has lost over 190 troops last year with most killed by shelling from separatists and by explosive devices.