The Dutch port of Rotterdam has seized 90,000 bottles of Russian vodka allegedly destined for North Korean leader Kim Jong-un and his top generals.

Customs officers nabbed the 3,000 cases of vodka on Friday in a vessel belonging to the Chinese company Cosco Shipping on a tip from the Russian foreign ministry.

They believe the intended recipient was Kim and military commanders.

The confiscation was followed by findings that a Russian tanker secretly transferred fuel to a North Korean ship at sea at least four times in 2017 and 2018, which would violate international sanctions over Pyongyang's nuclear missile programme.

Two crew members told Reuters that the ship left Vladivostok ostensibly for China, but instead met up with the North Korean tanker Chon Moyng-1 at night while it was not transmitting its position.