Al Jazeera has condemned calls made by US legislators for the media network to register as a foreign agent.

Josh Gottheimer and Lee Zeldin, two US legislators, have co-authored a letter claiming that Doha-based Al Jazeera is used to "incite violence" and broadcast "hateful, extremist content".

Rebutting the claims, Al Jazeera Media Network, in a statement on Thursday, said: "It is shocking to hear calls being made by a number of US lawmakers to register Al Jazeera as a foreign agent under the Foreign Agent Registration Act".

The network "has provided multi-award winning news coverage and current affairs programmes for more than 21 years" since its founding in 1996, the statement said.

Foreign Agent Registration Act, or FARA, is a little-enforced 1938 US law that was originally passed to combat Nazi propaganda.

It has since been used to keep track of foreign influence on US politicians through mandatory filings of employee contracts, contracts between the organisation and foreign governments, correspondence or any other documents that could be used to influence US policy.

The law has received more attention recently because the investigation into possible collusion between US President Donald Trump's 2016 campaign team and Russian officials.

Robert Mueller, the special counsel heading that investigation, has charged two former Trump campaign officials with violating FARA.

In November, Russia-backed media RT and other outlets were required to register under the law.

US politicians have also called for China-owned media networks to register.

These calls have caused concern that the US is imposing restrictions on freedom of speech, a right guaranteed under the First Amendment of the US Constitution.

"We urge democratic forces all over the world, especially in United States, to stand with free media institutions to promote and protect the values of democracy, liberty, human rights, freedom of media and the right to free speech," Al Jazeera Media Network said.

"Don't shoot the messenger, journalism is not a crime."