Two women and a man entered the site of the ancient Greek stadium and temple where the Olympic flame is traditionally lit and which had been sealed off for days by police.

They unfurled a banner reading "No Genocide Games" and a Tibetan flag seconds after the torch was lit by an actress playing the role of high priestess at the Temple of Hera a few metres away, and shouted as officials looked on.

The ceremony itself, also watched by Greek President Katerina Sakellaropoulou, was not interrupted and the three activists, who did not reach the actual stadium or temple, were led away by police.

The Chinese capital will become the first city to host both the Winter and Summer Games when it stages the February 4-20 event but protests and calls for boycotts over the country's human rights record have marred the run-up.

Four other protesters were detained outside the stadium an hour before the ceremony and taken to a local police station while two more were arrested in Athens on Sunday after protesting at the Acropolis monument.

Rights groups and US lawmakers have called on the International Olympic Committee (IOC) to postpone the Games and relocate the event unless China ends what the United States deems ongoing genocide against Uyghurs and other Muslim minority groups.

Chinese authorities have been accused of facilitating forced labour by detaining around a million Uyghurs and other primarily Muslim minorities in camps since 2016.

China denies wrongdoing, saying it has set up vocational training centres to combat extremism.

"The Olympic Games cannot address all the challenges in our world," IOC President Thomas Bach said in his address inside the ancient stadium before the protest.

"But they set an example for a world where everyone respects the same rules and one another. They inspire us to solve problems in friendship and solidarity."

It was the second time, after the Beijing 2008 Games, that the torch lighting ceremony was disrupted by protests by human rights activists.

Australian Associated Press