UPDATE 4-Climate change activists target BlackRock in London

* BlackRock targeted by Extinction Rebellion

* Activists say 2,799 people arrested globally in past week

* Reuters analysis finds index funds rarely act on climate

* Police ask climate activists to cease all assembly (Adds police statement, paragraphs 6-8)

By Guy Faulconbridge and Matthew Green

LONDON, Oct 14 (Reuters) - Climate activists targeted BlackRock, the world's biggest asset manager, in London on Monday, demanding that major financial institutions starve fossil fuel companies of the money they need to build new mines, wells and pipelines.

Extinction Rebellion, which uses civil disobedience to highlight the risks posed by climate change and the accelerating loss of plant and animal species, is midway through a new two-week wave of actions in cities around the world.

Activists thronged the financial heart of London on Monday, unfurling banners, addressing passersby by megaphone or blocking streets around locations including BlackRock, the Bank of England, Bank of China and Barclays.

At BlackRock, volunteers glued themselves to the doors while others staged a mock dinner party with rolled-up banknotes on their plates, a Reuters reporter said.

"The City of London is a preeminent nexus of power in the global system that is killing our world," said Carolina Rosa, spokesperson for Extinction Rebellion.

Police later called for a halt of all assembly linked to the Extinction Rebellion in London and said that anyone who fails to do so will be liable for arrest and persecution.

"These conditions have been imposed due to the continued breaches of the section 14 condition previously implemented, and ongoing serious disruption to the community," Deputy Assistant Commissioner Laurence Taylor said.

"Officers have begun the process of clearing Trafalgar Square and getting things back to normal," Taylor added.

BlackRock declined to comment.

Extinction Rebellion wants to cause enough disruption to force governments to rapidly cut carbon emissions and reverse the collapse of ecosystems to avert the worst of the devastation scientists project if business as usual continues.

Critics say the group is proposing what amounts to the overthrow of capitalism without any clear idea of what would replace it, and that the world's energy needs cannot be met without fossil fuels.

Extinction Rebellion said that 1,336 people had been arrested in London since it launched its actions a week ago. A further 1,463 people have been arrested in 20 cities in countries including the Netherlands, Belgium, the United States, Australia, Canada and New Zealand.

"CRIMINAL DAMAGE"

While activists have long targeted fossil fuel companies, a growing global climate protest movement is increasingly scrutinising the role fund managers, banks and insurance companies play in enabling oil and gas extraction.

Emily Grossman, a British science broadcaster and expert in molecular biology who joined the protest outside BlackRock, said that financing fossil fuel projects was undermining the goals of the 2015 Paris Agreement to limit global warming.

"This is criminal damage that they are doing to our lives and to the lives of our children and it has to stop," said Grossman.

Major oil companies have approved $50 billion of projects since last year that run contrary to the goals of the Paris Agreement, according to an analysis published last month by financial think-tank Carbon Tracker.

Fossil fuel companies say they need to invest in new projects to meet future demand for energy, particularly in fast-growing regions such as Asia.

Climate protesters want to pressure index fund firms such as BlackRock because the sector, which now controls half the U.S. stock mutual fund market, has enormous power to influence companies in which they invest trillions of dollars.

The leading U.S. index fund firms, BlackRock, Vanguard Group and State Street Corp, rarely use that clout, a Reuters analysis of their shareholder-voting records found this month. (Writing by Guy Faulconbridge and Matthew Green; additional reporting by Simon Jessop in London and Akshay Balan in Bengaluru; Editing by Michael Holden, Ed Osmond and Grant McCool)