Image copyright Getty Images Image caption Donald Trump has been hitting back at Fox host Megyn Kelly since she hosted the first Republican debate last August

Fox News has fired back at Republican presidential candidate Donald Trump for his refusal to participate in their debate on Thursday night.

The network said in a statement that Mr Trump's decision is "unprecedented" and accused him of "terrorising" debate host Megyn Kelly.

Mr Trump clashed with Ms Kelly at a Fox News debate last year and had demanded she be removed from Thursday's panel.

His decision to pull out has been mocked by his Republican rivals.

The debate is the final one before the first real test of the election campaign, the Iowa caucus on Monday when voters in the state pick their presidential nominee.

"Capitulating to politicians' ultimatums about a debate moderator violates all journalistic standards, as do threats," the Fox News network said in a statement.

Analysis - Anthony Zurcher, BBC North America reporter

There are plenty of reasons Donald Trump's last-minute withdrawal from the Republican debate could be a bad move.

He's on the verge of winning the Iowa caucuses, so why shake things up now? His past debate performances haven't hurt him, and his most recent was probably his best.

What's to gain from squabbling with the most powerful conservative media company in the nation? Already his opponents are blasting him for being afraid of a fight, with Ted Cruz's campaign labelling him "Donald duck".

Yet every time it seems like Mr Trump has made a grievous miscalculation that - at last - will sink his campaign, it ends up as either brilliant strategy or his political armour is just too strong.

So maybe this will work out for the New Yorker. He's dominating the headlines once again. And his plan to hold a rally to support wounded veterans, while his opponents aim their criticisms at an empty lectern, could prove a winning contrast.

Did Mr Trump just turn the whole Fox Thursday night event into a "kids' table" debate?

Image copyright Getty Images Image caption Trump has ignited the Republican race and leads the field

"We're not sure how Iowans are going to feel about him walking away from them at the last minute, but it should be clear to the American public by now that this is rooted in one thing - Megyn Kelly."

It added: "We can't give in to terrorizations toward any of our employees."

Ms Kelly accused the New York billionaire of misogyny in the first debate last August and he responded the next day by accusing her of having blood "coming out of everywhere". He denied he was referring to menstruation.

Mr Trump, who leads the Republican field, quit the debate on Tuesday night after Fox put out a sarcastic statement that questioned his ability to deal with Russian President Vladimir Putin.

Fox responded by accusing Mr Trump of "viciously attacking" Ms Kelly, threatening her and spending four days trying to get her removed.

Republican presidential candidate Senator Ted Cruz mocked Mr Trump for his announcement.

He challenged him to a one-on-one debate and taunted him on Twitter using the hashtag #DuckingDonald.

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