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Joe Biden has got straight to work in the White House, hours after being sworn in as the 46th president of the United States.

"There is no time to waste when it comes to tackling the crises we face," he tweeted following his inauguration.

President Biden signed 15 executive orders to reverse a number of decisions made by Donald Trump's government.

They include action on tackling the coronavirus pandemic, climate change, racism and immigration.

An executive order is a written law introduced by the president that doesn't need to be approved by other US politicians.

A number of rules will be introduced to tackle the coronavirus pandemic, which has claimed more than 400,000 lives in the US.

There will be an order to wear masks and practise social distancing on all national government property.

A new office will be set up to better organise the response to the pandemic and to help roll out vaccines across the country - a target has been set of vaccinating 100 million people in 100 days.

The US will also stop the process - begun by the Trump administration - of withdrawing from the World Health Organization (WHO), the United Nations agency responsible for global public health.

Mr Biden has also promised to make the fight against climate change a top priority of his administration.

He signed an executive order beginning the process of rejoining the 2015 Paris climate agreement, from which Mr Trump formally withdrew the US last year.

Mr Biden has also cancelled the presidential permit - approved by Mr Trump - given to the Keystone XL Oil Pipeline, which environmentalists and Native American groups have protested against for more than a decade.

The burning of fossil fuels like oil are used to power factories, buildings and transportation. But they release carbon dioxide and other substances into the atmosphere, which trap heat from the sun and warm up the Earth.

Mr Biden has ended the Trump administration decision to build a border wall between the US and Mexico.

He also ended a travel ban on some majority-Muslim countries.

Other orders cover race and gender equality, including work to "root out systemic racism" by devoting funds to "underserved communities".

A statement outlining all of these executive orders said President Biden "will take action - not just to reverse the gravest damages of the Trump administration - but also to start moving our country forward".