Republican Donald Trump on Wednesday claimed victory in the 2024 US presidential contest after Fox News projected that he had defeated Democrat Kamala Harris, which would cap a stunning political comeback four years after he left the White House.

As jubilant supporters cheered and chanted "USA", Trump took to the stage at his campaign headquarters in Florida along with his wife Melania and several of his children.

"We are going to help our country heal," the Republican former president said. "It's a political victory that our country has never seen before."

Addressing a roaring crowd of supporters at the Palm Beach County Convention Centre, Trump said "America has given us an unprecedented and powerful mandate."

Other news outlets had yet to call the race for Trump, but he appeared on the verge of winning after capturing the battleground states of Pennsylvania, North Carolina and Georgia and holding leads in the other four, according to Edison Research.

Harris did not speak to her supporters, who had gathered at her alma mater Howard University. Her campaign co-chair, Cedric Richmond, briefly addressed the crowd after midnight, saying Harris would speak publicly later on Wednesday.

“We still have votes to count," he said.

The mood shifted had shifted sharply at the watch party as the results came in.

"I am scared," said Charlyn Anderson. "I am anxious now. I am leaving, my legs can barely move."

In contrast, the celebrations intensified at Trump's Mar-a-Lago resort in Florida and the watch party nearby.

Tech tycoon Elon Musk, who has backed Trump and stands to lead a government efficiency commission under him, posted a picture of himself with the Republican.

"Game, set and match," Musk said on X, the social media network he owns along with the Tesla electric vehicle firm and the Space X company.

The former president was showing strength across broad swaths of the country, improving on his 2020 performance everywhere from rural areas to urban centres.

In a further blow to Democrats, Trump's Republican Party also seized control of the Senate, flipping two seats to overturn a narrow Democratic majority. Neither party appeared to have an edge in the fight for control of the House of Representatives where Republicans currently hold a narrow majority.

Trump went into Election Day with a 50-50 chance of reclaiming the White House, a remarkable turnaround from January 6, 2021, when many pundits pronounced his political career to be over.

That day, a mob of his supporters stormed Congress in a violent attempt to overturn the results of the 2020 election.

Trump picked up more support from Hispanics, traditionally Democratic voters, and among lower-income households that have keenly felt the sting of price rises since the last presidential election in 2020, according to exit polls from Edison.

Trump won 45 percent of Hispanic voters nationwide, trailing Harris with 53 percent but up 13 percentage points from 2020.

About 31 percent of voters said the economy was their top issue, and they voted for Trump by a 79-to-20 margin, according to exit polls.

Some 45 percent of voters across the country said their family's financial situation was worse off today than four years ago, and they favoured Trump 80 to 17 percent.

Global investors were increasingly pricing in a Trump win. US stock futures and the dollar pushed higher, while Treasury yields climbed and bitcoin rose – all flagged by analysts and investors as trades that favour a Trump victory. (Agencies)