It means she will be in charge for next year's delayed Tokyo 2020 Olympics and Paralympics.

Media reports from Japan have declared Koike, the first female Governor of the city, successful in defending her position amid the COVID-19 crisis.

She was the clear favourite and was initially elected after a landslide win in 2016.

According to opinion polls, the 67-year-old's handling of the virus has been popular with residents, unlike that of Japan's Prime Minister Shinzō Abe who has faced criticism during the pandemic.

Her term will now extend to 2024 and will cover the period of the rescheduled Olympic Games and Paralympic Games, now due to take place between July and September in 2021.

Koike, who ran as an independent, defeated 21 other candidates to the position including former head of the Japan Federation of Bar Associations Kenji Utsunomiya, former actor and leader of the anti-establishment party Reiwa Shinsengumi, Tarō Yamamoto, and former vice-governor of the Kumamoto Prefecture, Taisuke Ono.

With 82.3 per cent of votes counted, Koike was confirmed the winning candidate with 60.3 per cent of the vote, ahead of Utsunomiya, Yamamoto and Ono, who all polled at over 10 per cent.

The Liberal Democratic Party, of which Abe is the leader, did not field a candidate for the election. 

Tokyo 2020 President Yoshiro Mori said he looked forward to working "even closer" with the Governor ahead of the Games next July.

Mori said: "Of the many candidates in this election, Governor Koike has made the Tokyo 2020 Games a centrepiece of her policies.

"As we have been working together on preparations for a successful Tokyo 2020 Games, I am reassured by her re-election and look forward to further strengthening our partnership.

"As we prepare for the Games, we are aiming for a simplified Games befitting a new era after going through these challenging times.

"We have thus begun thorough discussions with stakeholders regarding streamlining and optimisation.

"I believe that Governor Koike's approach is the same as ours in gaining the understanding and consideration of the citizens of Tokyo and Japan in the delivery of the Games.

"The Tokyo 2020 Games will symbolise humanity's solidarity and unity in overcoming the threat of COVID-19 and many people are looking forward to a Games that will forever remain in their memories.

"I hope for even closer collaboration with Governor Koike, as leader of the host city of Tokyo, as we work to deliver the Games."

Koike was praised for requesting Tokyo residents stay at home ahead of Abe's declaration of a state of emergency in May, and has appeared regularly on television during the COVID-19 crisis.

Despite Koike's handling of the pandemic generally being approved, Tokyo has witnessed four straight days where new daily cases of COVID-19 have been above 100.

This follows the reopening of businesses on June 19 by the Tokyo Metropolitan Government, with today's new cases tally totalling 111.

Koike has said that she will coordinate with the International Olympic Committee over the hosting of Tokyo 2020 next year, and has also pledged to respond "firmly" to any second wave of COVID-19.

Tokyo 2020 was a big campaigning issue, with a survey last month revealing that more than half of Tokyo residents objected to the Games going ahead next year.

Yamamoto said he would cancel Tokyo 2020 if elected.

International Olympic Committee President Thomas Bach also extended his congratulations to the re-elected Governor.

Bach said: "The result is a reflection of the great confidence the citizens of Tokyo have in her leadership during these challenging times.

"I would like to express my thanks and gratitude for her steadfast commitment and her personal support to ensure the success of the Tokyo 2020 Games, the first-ever postponed Games in history.

"While organising postponed Games is an unprecedented challenge for all of us, we are fortunate to have partners like Governor Koike and the Tokyo Metropolitan Government by our side, who share our determination to make the postponed Olympics a symbol of hope and resilience for all humankind to overcome this pandemic.

"In these unprecedented times, the Games will take on an even greater significance as a celebration of unity and solidarity for the entire world."

Koike's projected 60 per cent vote share is up on her 44.49 per cent share from her initial election in 2016 where she won by more than 17 per cent.