Japan will open a mass vaccination centre in central Tokyo next month, officials said on Tuesday, part of the country's bid to speed up its COVID-19 inoculation campaign as the Olympic Games looms.

No decision has been made on which vaccine will be used or how many people will get shots each day, Chief Cabinet Secretary Katsunobu Kato told reporters.

"We will announce the details once the defence ministry and local authorities have come up with a plan," Kato said. The government will also support innoculation efforts in Osaka, in western Japan, he added.

Japan imposed a third state of emergency in its major population centres on Sunday, as the country attempts to combat a fourth wave of infections with just 87 days remaining until the Olympics is scheduled to begin.

The Defense Ministry tweeted it had been asked by Prime Minister Yoshihide Suga to set up the centre by May 24 with plans for it to operate for three months. The facility will service residents in the capital and the surrounding prefectures of Saitama, Chiba, and Kanagawa.

The Nikkei newspaper reported on Sunday the Tokyo centre would inoculate about 10,000 people a day, while the Kyodo news service on Monday reported the government planned to use the Moderna Inc (MRNA.O) COVID-19 vaccine.

Japan began vaccinating its sizable elderly population this month but only about 1.5% of the country's entire 126 million population has been vaccinated, according to a Reuters tracker.

Officials have so far been dependent on limited imported doses of Pfizer Inc's (PFE.N) vaccine.

However, vaccine minister Taro Kono has said he expects the programme to pick up in May when Pfizer shipments are due to accelerate. Domestic regulators are expected to make a decision next month on Moderna's vaccine, of which the government has arranged to buy 50 million doses. The government has also arranged to buy 120 million doses of AstraZeneca Plc's (AZN.L) vaccine, which is also in the approval process.

Japan has recorded about 564,000 COVID-19 cases, including 9,969 deaths.