A Japanese government panel on Thursday recommended approval of Moderna and AstraZeneca's Covid-19 vaccines, as criticism mounts over the slow start to inoculations with just two months until the Olympics.

The Pfizer-BioNTech formula is currently the only vaccine licensed for use in Japan, where less than two percent of the population of 125 million are so far fully vaccinated.

A health ministry official told AFP that the panel "concluded it has no objection" to the two vaccines' approval, clearing the way for the formal government green light, expected on Friday.

Two mass vaccination centres operated by the military in Tokyo and Osaka will open next week and are expected to administer the two-shot Moderna vaccine, initially to the elderly.

Japan's government is under pressure over its comparatively slow start to vaccinations, with strict rules that required additional domestic trials and complicated bureaucracy.

Only medical workers and the elderly are so far eligible, with no timeframe yet for expanding the rollout.

-Vaccination is a powerful card among coronavirus measures... the entire government is trying to form a system in which we can vaccinate as many people as possible- Prime Minister Yoshihide Suga told reporters on Thursday.

The decision comes after International Olympic Committee chief Thomas Bach said at least three-quarters of athletes and team members staying at Tokyo's Olympic village will be vaccinated before the Games, which open on July 23.

Organisers insist the event can be held safely this summer, although public opinion remains largely opposed as infections surge in Japan, with regions including Tokyo currently under a virus state of emergency.

While the government says the Olympics do not factor into its vaccine rollout plan, Suga has said they aim to finish inoculating the over-65s by the end of July.

Japan has agreements with drug firms to provide enough vaccine doses for its entire population, including Moderna doses for 25 million people and Pfizer for 97 million people.

It has ordered AstraZeneca doses sufficient to vaccinate 60 million people.

Earlier this month, the CEO of Japan's top drugmaker Takeda, which has an agreement with Moderna to distribute its vaccine, said discussions were ongoing to increase the total number of Moderna doses imported to 100 million.

-It shows that there is a great need for these vaccines in Japan- Christophe Weber said.