Human rights activists unfurled a banner reading "No Genocide Games" and called for a boycott of the Beijing 2022 Winter Olympics during the torch-lighting ceremony on Monday.
Two women and a man sneaked past a tight police cordon and entered the archaeological site of the ancient Greek stadium and temple where the Olympic flame is traditionally lit and which had been sealed off for days.
They waved 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.
The three protesters shouted for a boycott of the Games in Beijing, as invited officials, including Greek President Katerina Sakellaropoulou and International Olympic Committee President Thomas Bach, looked on.
The ceremony itself was not interrupted, as had been the case for the 2008 Beijing summer Games, and the activists, who did not reach the actual stadium or temple, were quickly led away by police.
The Chinese capital will become the first city to host both the Winter and Summer Games when it stages the Feb. 4-20 event but protests and calls for boycotts over the country's human rights record have marred the run-up.
Four other activists were detained by police outside the stadium an hour before the ceremony and taken to the local station. They had not been charged yet.Two more were arrested in Athens on Sunday after protesting at the Acropolis monument.
Activists are planning more protests and a news conference on Tuesday when the flame will be official handed over to Beijing Games organisers in Athens.
"The Olympic Games cannot address all the challenges in our world," Bach said in his address inside the ancient stadium prior to 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."
Rights groups and U.S. 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.
It was the second time, after the Beijing 2008 Games, that the torch lighting ceremony was disrupted by protests by human rights activists, who had stormed that ceremony and repeatedly disrupted the international torch relay that followed.
"Under the robust leadership of the Chinese government... we can and will deliver a streamlined, safe and splendid Olympic Games to the world," Beijing Games vice president Yu Zaiqing said.