Reporters from three media outlets have been barred from entering the White House, hours after a federal judge ruled that President Donald Trump's ban on their access should be temporarily lifted.

Employees from CNN, Politico and MS Now reported being denied entry on Thursday morning, with some having their credentials confiscated, while others were granted access.

Lawyers for the outlets have requested an emergency court hearing, saying the White House "repeatedly violated" the order to restore press access.

Judge Timothy Kelly overturned the ban in the early hours of Thursday, ruling that it "likely violated their constitutional due process rights".

Trump originally said he decided to ban the outlets because they were spreading "fake news". The White House later cited national security as grounds for barring them.

It was unclear whether the refusal to admit some reporters on Thursday morning was because of an administrative lag as the White House potentially worked to comply with the judge's order.

The standoff is expected to impact TV coverage as Trump welcomes Chinese President Xi Jinping to the White House on Thursday morning ahead of a state dinner.

CNN said some of their reporters had been denied entry, including senior White House reporter Betsy Klein. But a producer was allowed to enter, the outlet reported.

Politico said one of its reporters was denied access to the White House on Thursday morning and had his press credentials confiscated.

MS NOW reported that its White House reporter Laura Barrón-López and a producer were denied access and had their passes taken, but another MS NOW producer was allowed entry.

The White House is yet to comment on the ruling, and lawyers acting for the president may take further legal action.