Tokyo elected the country's former defence minister, Yuriko Koike, as its first female governor on Sunday, media exit polls show.

"I will lead Tokyo politics in an unprecedented manner, a Tokyo you have never seen," Koike, 64, told cheering supporters in a hoarse voice after two weeks of campaigning.

Koike will be dealing with Tokyo's troubled preparations for the 2020 summer Olympics, which have been plagued by a series of embarrassing scandals and soaring costs.

Tokyo's last governor resigned amid financial scandals.

Koike's four-year term will extend until just after the Olympic Games start and her performance in the run-up will be scrutinised closely.

A key challenge of her governorship will be getting to grips with swelling preparation costs for the Games, which are seen as possibly double or triple the reported original forecast of 730bn yen ($7.14bn).

Plans for the Tokyo Games have been overshadowed by allegations of corruption, and French prosecutors have launched an investigation into alleged bribes linked to Tokyo's bid. 

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Other key issues in the election were Tokyo's dire childcare shortage and overseeing disaster response plans due to perennial earthquake threats to the capital.

Koike, a ruling Liberal Democratic Party (LDP) politician, ran without her party's endorsement, which spurned her for failing to seek approval before announcing her candidacy.

She has compared herself to US presidential candidate Hillary Clinton and was once seen as having the best chance to be Japan's first female prime minister. But she was defeated when running in 2008 for leadership of the LDP.

As a former TV anchorwoman, she speaks fluent English and Arabic - the latter acquired as a student in Cairo - and served as both defence minister and environment minister.

Source: Al Jazeera and agencies