From behind his desk in the Oval Office, President Donald Trump signed a flurry of executive orders and decrees aimed at cracking down on immigration.

From an order tackling the definition of birthright citizenship, to an order declaring the illegal immigration at the border a national emergency, Trump swiftly made moves on his promises to tighten the US-Mexico border.

But some of those orders – particularly any order that aims to change the definition of birthright citizenship – are likely to face steep legal opposition.

Trump had previously vowed that the “destructive” policies of the Biden White House would be gone “within five minutes”.

Hours earlier, thousands of would-be migrants had their immigration appointments cancelled after the new administration scrapped CBP One, an app used to book appearances at ports of entry at the border.

In his inaugural address, Trump vowed that “all illegal entry will be halted” and that millions of “criminal aliens” will be deported.

He also signed an order declaring Mexican drug cartels terrorist organisations.

At a previous event at Washington’s Capital One Arena, Trump formally revoked nearly 80 executive actions – which he described as “radical” – from the Biden administration.

“I have no higher responsibility than to defend our country from threats and invasions,” Trump said in his inaugural address at the US Capitol earlier in the day.

As part of the broader plan, Trump administration officials said the president would direct the Department of Defense to “seal the border” and devote additional resources and personnel, including counter-drone capabilities.