* States of emergency declared from April 25 to May 11
* Curbs cover almost a quarter of Japan's population
* Olympic Games start in three months (Updates with PM Suga)
By Chang-Ran Kim
TOKYO, April 23 (Reuters) - Japan declared "short and powerful" states of emergency for Tokyo, Osaka and two other prefectures on Friday as the country struggles to contain a resurgent coronavirus pandemic three months before the Olympics.
The government will require restaurants, bars and karaoke parlours serving alcohol to close, and big sporting events to be held without spectators from April 25 to May 11, Economy Minister Yasutoshi Nishimura said.
Breaching the restrictions will in some cases carry penalties, he said.
"We absolutely have to limit the movement of people, and we have to do it decisively. We need powerful, short and focused measures," he said, asking people to remember the lockdowns of last spring and stay at home.
Prime Minister Yoshihide Suga said Japan would take measures to ensure it could safely hold the Olympics this summer. The pandemic has sharpened focus on whether the Games can or should go ahead.
"It is feared that contagion in major cities will spread across the whole country if we take no measures," Suga said.
Under the measures, department stores, cinemas and other commercial facilities larger than 1,000 square metres (1,200 square yards) will have to close and companies will be asked to make allowances for people to work from home. Schools will remain open.
The state of emergency - a third round for Japan that also includes Kyoto and Hyogo - will cover nearly a quarter of the population and last through the looming "Golden Week" holidays, dealing another blow to the tourism and services industries.
Tokyo Governor Yuriko Koike said the government would ask for illuminations and neon signs to be turned off.
"It will be dark at night," she told a news conference, and asked non-residents to refrain from entering Tokyo if possible.
Japan has avoided an explosive spread of the pandemic experienced by many countries. There have been about 550,000 cases and 9,761 deaths, significantly lower numbers than in other large economies.
But the latest rise in infections has stoked alarm, with a surge in a mutant variant and a critical shortage of medical staff and hospital beds in some areas. Japan's vaccination drive remains sluggish.
Organisers of the Tokyo Motor Show on Thursday cancelled the marquee event for this year. Tokyo 2020 organisers said on the same day that a policeman who worked with the torch relay had tested positive for the virus, a first for the event.
Tokyo 2020 President Seiko Hashimoto said organisers were not considering cancelling.
"We, as Tokyo 2020, continue to wish for the swift return to normalcy and will continue to work closely with the relevant parties to make sure a safe and secure Olympics can happen," she told a news conference.
Tokyo reported 759 new infections on Friday, down from 861 a day earlier when the tally was the highest since Jan. 29.
Several other prefectures remain in a "quasi-emergency" state of targeted infection controls. Nishimura said the duration would be extended to May 11 for some. (Reporting by Chang-Ran Kim, Yoshifumi Takemoto, Sakura Murakami and Elaine Lies; Editing by David Dolan, Sam Holmes, Michael Perry, Catherine Evans and Timothy Heritage)