A ceremony was held on Saturday to mark the completion of the Tokyo Aquatics Centre, which will host swimming competitions in next year's Olympic and Paralympic Games.

The metropolitan government spent about 540 million dollars to build the venue, where 15,000 seats, including temporary ones, will be set up for the games.

A group of Japanese researchers have discovered a new species of marine worm in the bay where Tokyo Olympic triathlon events are scheduled.

Researchers from the National Institute of Polar Research and Toho University said they discovered what they believe to be a new scavenger species of Ophryotrocha worm.

The Tokyo Metropolitan Government has started work to improve water quality at a venue of this year's Olympic and Paralympic Games after higher-than-acceptable levels of E. coli bacteria were detected there last year.

Odaiba Marine Park is the intended venue for the swimming leg of the triathlon for the Tokyo Games.