Around 700 migrants and their supporters joined the demonstration, with some pushing into the historic complex at around midday on Friday, a member of the Chapelle Debout collective said. Footage posted on Twitter from inside the building's main dome showed hundreds of people waving papers in the air shouting “Black vests, black vests!” and “What do we want? Papers!”
The so-called “Black Vests” is a Paris-based migrant association that takes its name from the “yellow vest” anti-government protest movement.
In a statement, the Black Vest protesters said they wanted “papers and housing for everyone”, describing themselves as “the undocumented, the voiceless and the faceless of the French Republic”.
“We don't want to negotiate with the interior minister and his officials any more, we want to talk to Prime Minister Edouard Philippe now!” they wrote.
They stayed there for several hours until they were calmly evacuated through a back entrance mid-afternoon, AFP correspondents said.
“All of the people who gained entry to the Pantheon have been evacuated,” Philippe tweeted early evening as a police source said 37 arrests had been made.
'Rule of law'
“France is a country based on the rule of law which means respect for the rules that apply to the right to remain, respect for public monuments and for the memory they represent,” he added.
Some leftist lawmakers came to the site to offer moral support to the migrants but Marine Le Pen, leader of the far-right National Rally, tweeted her indignation.
“It is UNACCEPTABLE to see protesting illegal aliens occupy, with wholesale impunity, this is the centre of the Republic,” Le Pen said.
“Expulsion should be the immigrants' future — that is the LAW,” she said. “The Pantheon is a symbol of great men. Inside there are symbols representing the fight against slavery. We are fighting against modern-day slavery,” said Laurent, an activist from French rights group Droits Devant.
“Many people have been living without rights for years. We have done this to ask the prime minister for an exceptional regularisation. There has never been such a thing since (Francois) Mitterrand took power” in 1981. “It's about time we had one.”
The “Black Vests” are known for staging headline-grabbing protests in support of the undocumented.
In June, they briefly occupied the headquarters of the Paris-based Elior Group which works in contract catering and property. And a month earlier, its activists occupied terminal 2F at the city's Charles De Gaulle airport against “Air France's collaboration” in the deportation of undocumented migrants.