Killer whales have been spotted in Tokyo Bay, prompting the Japan Coast Guard to warn ships passing through the area to avoid the cetaceans.

It is very rare for killer whales to be seen in Tokyo Bay.

A patrol ship belonging to the Yokohama chapter of the JCG confirmed the sighting of a group of killer whales in waters 6 km south of Kanaya Port in Futtsu, Chiba Prefecture, at around 10 a.m. on Monday.

A fishing boat then alerted authorities to "three or four" killer whales some 5 km southwest of the port, at 11 a.m. on Tuesday.

Video footage of the animals provided by the JCG show them swimming elegantly, undeterred by nearby ships.

The JCG's Yokohama chapter issued a warning to the ships in the area at 12:30 p.m. on Tuesday.