Paris A topless female protester with "Fake Peacemaker" scrawled across her chest ran at the motorcade carrying US President Donald Trump along the Champs Elysees in Paris before a ceremony on Sunday to mark 100 years since the end of World War I.
One woman easily breached right security along Paris' famous boulevard, coming within a few metres of Mr Trump's motorcade before she was seized by police.
A second topless protester was detained as she attempted to clear barricades that had been erected for the event. Femen claimed three protesters breached the barrier.
The incident is likely to raise questions about security at the event attended by some 70 world leaders.
The radical feminist activist group Femen, based in Paris, said it was behind the stunt. Femen, an anti-war group with origins in Ukraine, frequently carries out shock protests against sexism, racism, homophobia and other social and political issues.
Paris police said they detained two people over the incident.
Femen group leader Inna Shevchenko tweeted a video of the incident and said the presence of Mr Trump and other world leaders, including Russian President Vladimir Putin and Turkish President Recep Tayyip Erdogan, had transformed the Armistice Day event "into a sad spectacle which is entertaining only for the criminals participating in it".
"They've come to celebrate peace but they're promoting war," she wrote, later adding: "Welcome war criminals."
The US Secret Service did not immediately respond to a request for comment about the security breach, which occurred just outside the Louis Vuitton flagship store.
The incident occurred shortly after other world leaders and dignitaries, led by French President Emmanuel Macron, walked down the Champs-Elysees avenue towards the armistice commemoration event.
Some leaders, including Mr Trump and Mr Putin, did not participate in the march, citing security concerns.