One of the victims of Sunday's blast aboard a vessel of the Mariupol Coastguard Detachment has died of the injuries, the press service of the Ukrainian Interior Ministry's Donetsk regional department has reported.

"The Police Department received a report at 6:30 p.m. that one of the six hospitalized victims has died. He was a civilian, a resident of Mariupol, aged 45," it said in statement circulated on Sunday.

Efforts continue to find the seventh crewmember - the boat commander, the police said.

The Ukrainian State Border Service earlier reported that a coastguard vessel, the UMC-1000 of the Mariupol coastguard detachment, "exploded at 2:20 p.m. on Sunday for an unidentified reason when it was leaving the base."