The International Olympic Committee (IOC) has warned athletes are not exempt from the strict COVID-19 rules in place at the Tokyo 2020 Olympic Games here after swimmers were seen taking off their masks and hugging other competitors on the podium.

IOC Presidential spokesperson Mark Adams urged athletes to follow the COVID-19 rules, which state Olympic participants must wear masks at all times, except for when competing, training, eating or sleeping.

They have been allowed to briefly take them off on the podium for 30 seconds for a photo opportunity, however.

Competitors at the Games have also been told to limit social contact with other athletes and avoid taking group photos on the podium.

Under the regulations for medal ceremonies, athletes have been told to stay on their own podium step and keep a distance from their fellow medallists.

All 12 athletes from Australia, Canada and the United States on the podium for the women's 4x100 metres freestyle relay did not have their faces covered and were spotted hugging.

The three medallists in the men's 400m individual medley - newly-crowed Olympic champion American Chase Kalisz, compatriot Jay Literland, who was second, and Australian Brendon Smith - were seen without masks.

Kalisz and Literland were also seen hugging each other following the victory ceremony.

"We would urge and ask everyone to obey the rules, whatever stakeholder you are," Adams said.

"It is not a nice to have, it is a must have, both for the sports and for everyone involved.

"It sends a strong message so please follow the playbooks.

"We understand there is excitement and we feel for the athletes but unfortunately we have had to make the rules stricter.

"These messages are constantly passed, not just to athletes.

"It is in our interests and the interests of everyone."

It is the second warning from the IOC regarding COVID-19 rule breaches at the Games after several athletes and officials who paraded in the Opening Ceremony were spotted without masks.

The IOC has said it will take action in cases of "blatant" breaches of the rules in the "playbooks", which organisers hope will ensure the delayed Games will be "safe and secure".

Health experts have claimed the Games could become a "super-spreader event", while Shigeru Omi, the Japanese Government’s top COVID-19 advisor, has warned staging the Olympics during a pandemic is "abnormal".

There have been reports in the Japanese media about accredited people breaking the rules by visiting bars and restaurants in tourist areas, leading to a clampdown on participants involved in the Games.

Tokyo is under a state of emergency until at least August 22 because of fears over rising COVID-19 cases, which led to the Japanese Government banning spectators from all Olympic events in the capital.