Japan has killed more than 200 pregnant whales, it has been reported.

According to the country’s Institute for Cetacean Research, 333 minke whales have been killed including more than 200 pregnant females as part of this year’s Antarctic whale hunt, the National Geographic reports.

It said that four ships returned from a 100-day expedition this week as part of a project aiming to conduct 'scientific' whaling activities.

The legitimacy of Japan's programme has been challenged previously by the International Court of Justice in 2014.

Commercial whaling activities have been banned by the International Whaling Commission since 1986, although an exemption remains for scientific studies.

Pictures reveal truth about Japan's 'scientific' whaling Show all 5 1 /5 Pictures reveal truth about Japan's 'scientific' whaling Pictures reveal truth about Japan's 'scientific' whaling 15404.bin This picture shows what the Australian government says is the slain carcass of a minke whale tied to the Japanese harpoon ship Yushin Maru 2 in the Antarctic waters AP Pictures reveal truth about Japan's 'scientific' whaling 15403.bin A minke whale and her calf are towed up the rear ramp of the Japanese whaling vessel Yushin Maru No.2 in the Southern Ocean REUTERS Pictures reveal truth about Japan's 'scientific' whaling 15399.bin Two whales are dragged on board a Japanese ship after being harpooned in Antarctic waters. The pictures, plastered over front pages and shown on television were taken from an Australian customs vessel tracking the whalers to gather evidence for possible legal action to stop the annual slaughter GETTY IMAGES Pictures reveal truth about Japan's 'scientific' whaling 15402.bin An Australian Customs Service boat from the patrol vessel Oceanic Viking, right, tracking the Japanese whaling in Antarctic waters. The Australian government stepped up it's public relations campaign against Japanese whaling in Antarctic waters by releasing images of whale killings to Australian media organisations AP Pictures reveal truth about Japan's 'scientific' whaling 15401.bin The whale is dragged on board a Japanese ship after being harpooned in Antarctic waters. GETTY IMAGES

Following the court’s ruling, Japan stopped its whaling activities for a brief period, but started again in 2015.

It changed its programme to make it more scientific and lowered its quota of whales by two-thirds – but the International Whaling Commission has not reached a consensus on whether it has met requirements, the National Geographic reports.