Climate protesters claim to have used superglue, chains and bike locks to block entrances to major insurance marketplace Lloyd’s of London.
Extinction Rebellion (XR) said more than 60 activists had been at the central London building since 7am on Tuesday to stop staff from entering the site and with the aim of closing the business for the day.
The environmental protest group said it is demanding that Lloyd’s of London stops insuring fossil fuels projects.
Lloyd’s, which describes itself as the world’s specialist insurance and reinsurance market, said it had advised staff not to go to the building on Tuesday.
A spokesman said: “Lloyd’s supports safe and constructive engagement on climate change and we’re continuing to work to support a responsible transition.
“In the interests of our people’s safety, we have advised Corporation employees and market participants not to come to the building today.
“The market remains open and trading is continuing online using our remote capabilities.”
By lunchtime on Tuesday, City of London Police said there had been no arrests and that officers were working to “facilitate peaceful protest”.
Commander Umer Khan, from the force, said: “Police officers are working with key partners and liaising with Lloyd’s to facilitate peaceful protest and to provide a proportionate response.”
XR said people had also scaled the outside of the building and unfurled banners, reading “End Fossil Fuels Now” and “Insure Climate Justice”.
The action comes after activists from Just Stop Oil and Extinction Rebellion caused Tower Bridge to be closed for several hours last Friday morning.
Police were called to the bridge after protesters occupied the famous landmark and unveiled a green banner with black writing reading: “End fossil fuels now”.
Of Tuesday’s demonstration, XR spokesperson Clare Walmsley said: “We’re here to demand an end to all new fossil fuel investments and insurance. By underwriting the world’s most deadly fossil fuel projects, they are creating climate chaos – floods, famine, wildfires and death.
“Insuring new oil and gas projects in the North Sea will do nothing to solve the cost of living crisis either. Instead, it locks us into a system that’s already pushing millions into poverty.”