Extinction Rebellion protesters have blocked one of Covent Garden’s busiest junctions on the first day of the group’s latest wave of protests targeting London.

At about midday, activists from the group chained themselves together to block the roundabout at Long Acre as a van pulled up with a pink table structure. It was quickly assembled and hundreds of other activists streamed to the roundabout.

Thousands of people gathered in Trafalgar Square earlier on Monday morning for an “opening ceremony”. Launching on the 230th anniversary of the Haitian revolution, XR’s “impossible rebellion” comes after the latest IPCC report suggested that human civilisation may have passed a crucial tipping point in carbon dioxide emissions.

Speaking from the steps in front of the National Gallery, Esther Stanford-Xosei, of the Stop the Maangamizi movement, called on activists to remember those living in developing countries, including Haiti, who were at the sharp end of the climate crisis.

“It’s really important for us here in London to begin this rebellion amplifying the voices of those communities in resistance,” she said.

Among those in the crowd was Fiona Gillespie, 58, from Cambridge. She said: “We have to be here because our governments have let us down, not just here but all over the world, [they’ve] let everybody down. They are so busy in their corporate bubbles helping out banks, businesses and the military imperial complex; they need to step out of their bubbles and smell the air because it’s full of smoke, and that’s the Earth burning.”

Protesters had begun a march from Trafalgar Square up Charing Cross Road, which was apparently a diversion to keep police busy while other activists built the structure on Long Acre.

Lautaro Illayux, from Colombia, spoke at the opening ceremony and marched carrying the Wiphala, the flag of indigenous Latin Americans. He said: “Communities in the global south have been in resistance to this death system since it was first established 500 years ago … there is no way out of this climate emergency without ancestral knowledge.”

The Metropolitan police were present. In a tweet, the force said: “A group of protesters have blocked the roads around Long Acre junction in #Westminster with a structure.

“Officers are on scene and specialist teams are being deployed. Road closures are in place.”