A federal judge in Maryland has indefinitely blocked US President Donald Trump's executive order to end birthright citizenship for undocumented immigrants and foreign visitors with temporary visas.

Judge Deborah L. Boardman from the United States District Court for the District of Maryland on Wednesday issued a preliminary injunction after a court hearing in Greenbelt, Maryland, in a case filed by civil rights groups seeking to block Trump's order.

The injunction applies nationally, Xinhua news agency reported.

"The Maryland lawsuit is one of at least six different federal cases brought against Trump's order by a total of 22 Democratic-led states and more than half a dozen civil rights groups," according to The Washington Post.

Trump signed the order hours after taking office on January 20. It directed federal agencies to halt recognition of citizenship for children born after February 19, if neither parent is a US citizen nor a permanent resident.

More than 20 states and civil rights groups immediately filed lawsuits challenging the order, calling it blatantly "unconstitutional".

On January 23, Senior US District Judge John Coughenour, a federal judge in Seattle, Washington state, temporarily blocked Trump's executive order for at least 14 days, as lawsuits in Washington state and elsewhere over Trump's action proceeded.

The 14th Amendment states that "all persons born or naturalised in the United States, and subject to the jurisdiction thereof, are citizens of the United States".

Trump's executive order argued that the 14th Amendment "has always" excluded from birthright citizenship persons who were born in the United States but not "subject to the jurisdiction thereof".

Trump's order was premised on the idea that anyone in the United States illegally, or on a visa, was not "subject to the jurisdiction" of the country, and therefore excluded from this category.

His opponents have argued that the 14th Amendment, which was ratified in 1868 as the United States sought to recover from the Civil War, has been settled law for over a century.

They have cited an 1898 US Supreme Court ruling in the case of a Chinese-American man named Wong Kim Ark, who was denied reentry to the United States because he was not a citizen.

The court affirmed that children born in the United States, including those born to immigrants, could not be denied citizenship.