WASHINGTON (REUTERS) - President Donald Trump on Monday (Jan 11) approved an emergency declaration for Washington that lasts through Jan 24, the White House said, after authorities warned of security threats to President-elect Joe Biden's inauguration next week.

The FBI has warned of armed protests being planned for Washington and all 50 US state capitals in the run-up to the Jan 20 inauguration, a federal law enforcement source said on Monday.

Threatened with more violence from Trump's supporters following last Wednesday's storming of the US Capitol, the FBI issued warnings for next weekend that run at least until Inauguration Day, the source said.

In other steps to safeguard the US capital, the National Guard was authorised to send up to 15,000 troops to Washington, and tourists were barred from visiting the Washington Monument until Jan 24.