TOKYO (Reuters) - Japanese authorities reviewing the cost of hosting the 2020 Summer Olympic Games will propose major changes for three planned venues - including moving rowing and canoeing some 400 km (240 miles) from the capital, media reported on Wednesday.

A Tokyo city government panel will release a report on its findings on Thursday after recently elected city governor Yuriko Koike ordered a review of ballooning costs, Kyodo News and other media said.

The proposed changes, which would require the approval of the International Olympic Committee (IOC) and each sport's international federation, are the latest in a series of setbacks and broken promises for organizers who had won the bidding largely on Japan's reputation for efficiency.

Tokyo's bid proposal said the majority of venues would be within 8 km (5 miles) of the Olympic Village in central Tokyo.

Kyodo said the panel would recommend that the construction of three venues - for volleyball, swimming, and rowing and canoe sprint - be reconsidered and that other, existing locations should be able to host those events.

Public broadcaster NHK said the panel would propose moving the venue for rowing and canoeing to Tome City in the northeastern prefecture of Miyagi, due to soaring costs and because not enough measures had been taken against wind and waves at the site in the original plan.

A Tokyo Metropolitan Government official declined to comment, saying while they were aware of the media reports they had yet to receive an official report from the panel.

Tokyo has already shifted the venues for several events out of the capital, including sailing and basketball. Cycling will take place in Shizuoka prefecture, about 200 km (125 miles) west of Tokyo.

Tokyo organizers have been grappling with a series of blunders. They were forced to scrap an initial design for the centerpiece National Stadium, site of the opening and closing ceremonies, because it was too expensive, and had to redesign the logo for the games following accusations of plagiarism.

Last month, Koike delayed the relocation of a Tokyo fish market, the Tsukiji market, which could jeopardize the construction of a road linking the Olympic Village and National Stadium.

(Reporting by Chris Gallagher and Elaine Lies; Editing by Robert Birsel)