Florida Governor Ron DeSantis has snatched second place in Iowa's caucuses, edging former UN ambassador Nikki Haley into third in a Republican contest dominated by Donald Trump.

Mr DeSantis had campaigned relentlessly in the state but he finished a long way behind the former president.

With nearly all the votes counted, Mr Trump has 51% of the vote, with Mr DeSantis on 21% and Ms Haley on 19%.

Iowa was the first state for Republican voters to make their White House pick.

Their election is called a caucus because people have to show up in person at a given location at a certain time in order to cast their vote.

The party's eventual nominee will challenge the Democratic choice, almost certainly President Joe Biden, in November's election.

He said he would "seal up the border" in the face of an "invasion" and called Joe Biden the country's worst president.

Registered Republicans braved sub-zero temperatures to gather on Monday evening across Iowa to cast ballots at churches, schools, gyms and community centres.

Mr Trump had been the overwhelming favourite to win Iowa and Glenn Jacobs, a former WWE wrestler who is campaigning for Mr Trump, had predicted the big win.

Speaking to the BBC an hour before voting began in Des Moines, he said the country was heading in the wrong direction, citing the border crisis and US intervention in the Middle East.

Mr Trump's son Eric told the BBC he hoped his father would wrap up the nomination by Super Tuesday on 3 March, when more than a dozen states will vote.

"We've [the country] become a laughing stock and it's got to stop," he said. "Hopefully it stops in Iowa."

At a high school in Davenport, in the eastern part of the state, Trump supporter Brian Romer gave an impassioned speech to his fellow Republicans in favour of the former president.

"The things that happen in this country are things that happen in communist countries," he said, referring to Mr Trump's criminal indictments. "We don't live in a free country anymore."

But both Mr DeSantis and Ms Haley, the former governor of South Carolina and US ambassador to the UN under President Trump, claimed on Monday night that the political wind was in their sails.

"They threw everything but the kitchen sink at us," Mr DeSantis said. "The media was against us. They were writing our obituary months ago.

"In spite of all of that… we've got our ticket punched out of Iowa."

"I like his [the Florida governor's] integrity, and the way he presents himself and - really - what he got done in Florida," he said.

Mr DeSantis spent most of his time and resources in Iowa, campaigning in all 99 counties and courting the rural state's influential bloc of evangelical voters.

But the conservative Florida governor could face tougher terrain in the more moderate state of New Hampshire, which holds its primary next week.

Ms Haley, who has an outside chance of beating Mr Trump in the state, claimed she had the momentum.

But her third-place finish seemed a disappointment for a candidate who was said to be surging ahead of the caucuses.

Hallie Still-Caris, who attended a caucus at Roosevelt High School in Des Moines, said Ms Haley had the best chance to win in November.

"I look at the other Republican candidates and President Biden," she said, "and I think she's electable. That's what we need - less drama and less chaos."

Biotech entrepreneur Vivek Ramaswamy announced he was suspending his presidential campaign after he seemed on course for a distant fourth-place finish. He endorsed Mr Trump.

In a post on X, Mr Biden noted that he seemed to be heading for a rematch with Mr Trump.

"But here's the thing: this election was always going to be you and me vs extreme Maga Republicans," the Democratic president wrote. "It was true yesterday and it'll be true tomorrow."