Extinction Rebellion protesters sprayed fake oil over the front of the Bank of England as part of action targeting financial institutions.
Demonstrators, dressed in black, staged the April Fools protest over the bank's role in the climate crisis.
They covered the front of the building with a substance made of black pond dye and a thickening agent called guar gum, to replicate oil.
"This bank is killing us," read a banner held up by one of those taking part in the action, while another placard said: "No more fossil fuels."
City of London police dispersed the activists and arrested five people, who were being held in custody.
Extinction Rebellion said its protest was aimed at those who are "recklessly endangering our future for profit".
"The world's 60 largest banks have funded the fossil fuel industry to the tune of $3.8 trillion since 2016," the group said.
"The action today highlights the Bank of England's failure to regulate these banks and points to the fact that it still holds investments consistent with 3.5C of warming by the end of the century."
Protests were also held at banks in Glasgow, Brighton, Cambridge and Cornwall, and in world cities including Paris, Brussels and Melbourne.
A recent report from Rainforest Action Network found that 60 of the world's largest commercial and investment banks spent $3.8trn (£2.75trn) on fossil fuels between 2016 and 2020.
In 2016, these banks pumped almost $3trn (£2.17trn) into fossil fuels, which increased by almost 10% in four years.
This is despite demand for fossil fuels decreasing last year due to the pandemic, the report says.
Extinction Rebellion's 'Money Rebellion' group said: "[The] Bank of England could regulate fossil fuel funding.
"They could make the banks integrate climate risks and could support green industry.
"But they don't."
A survey of economic experts published this week found that failing to address climate change immediately could cost the global economy $1.7trn (£1.24trn) a year by 2025.
The Bank of England declined to comment.
Sky News is set to launch the first daily prime time news show dedicated to climate change.
Hosted by Anna Jones, The Daily Climate Show will follow Sky News correspondents as they investigate how global warming is changing our landscape and how we all live our lives.
First airing on Wednesday 7 April, the show will also highlight solutions to the crisis and show how small changes can make a big difference.