Tokyo, Japan - The Tokyo Olympics were opened on Friday a year behind schedule by Japan's Emperor Naruhito and tennis star Naomi Osaka lit the cauldron in the culmination of a low-key ceremony in an all but empty stadium against the backdrop of the coronavirus.

The emperor and other dignitaries wore face masks just as the athletes and most others involved in the three-and-a-half hour show likely watched by billions around the world on television.

A minute's silence was observed for the victims of the pandemic which had forced the first-ever postponement of an Olympics, by one year.

Groups of protesters gathered outside the arena as the staging of the Games during the health crisis is opposed by a large majority of the Japanese people.

But the International Olympic Committee (IOC) and Japanese politicians and organizers had pressed on with the Games, to be held largely behind closed doors and amid a strict hygiene protocol.

"Today is a moment of hope," IOC president Thomas Bach said in his welcome speech.

"Yes, it is very different from what all of us had imagined. But let us cherish this moment because finally we are all here together," he said, naming solidarity "the light at the end of the dark tunnel of this pandemic."

Bach also thanked the Japanese people in their own language for making the Games possible.

The emperor formally declared the Games of the 32nd Olympiad open before Japan-born four-time grand slam champion Osaka, who has a Japanese mother and a father from Haiti, lit the cauldron in the conclusion of a torch relay also heavily marred by the virus.

The 23-year-old is one of the big gold medal hopes for the hosts, but has not played in two months since withdrawing from the French Open and then citing mental health problems.

Only just under 1,000 people were admitted to the 68,000-seat National Stadium, with foreign dignitaries including first lady Dr. Jill Biden and French president Emmanuel Macron.

The ceremony paid tribute to athletes training in pandemic conditions, with a runner on a treadmill and a cyclist and rower on their machines in the vast arena.

Japanese heritage was celebrated by hundreds of performers in tightly choreographed formation, and the host city of Tokyo highlighted.

The Tokyo 2020 emblem was shown in the stadium, and above it in the sky by 1,824 drones; and artists from all continents performed the famous Imagine song from John Lennon and his Japanese wife Yoko Ono.

There was also a homage to the pictograms which were invented for the first Tokyo Games in 1964.

The two-hour-long parade of nations, traditionally started by the first modern Olympic hosts Greece and completed by hosts Japan, saw most of the 206 teams with two flag bearers instead of one as the IOC is promoting gender equality.

They included Jamaican sprint star Shelly-Ann Fraser-Pryce and the face of the Refugee Team, Syria's Yusra Mardini. Tongan Pita Taufatofua only sported a loin cloth apart from his mask and was as well oiled up, as five years ago in Rio.

Teams marched in vastly smaller numbers than in the past because caution prevailed amid almost 100 positive coronavirus tests in the Olympic bubble in Japan, including several athletes.

Three male-female duos took the Olympic Oath, which now also includes an anti-discrimination passage, together for the officials, judges and around 11,000 athletes who will contest 339 medal events across 50 disciplines in 33 sports until August 8.