Former US President and 2024 presidential hopeful Donald Trump is projected to win the Republican primary in South Carolina, beating his rival Nikki Haley in her home state where she previously served as a governor, US media projections showed.

"This was a little sooner than we anticipated, and an even bigger win than we anticipated," Trump said on Saturday shortly after polls closed at 7 p.m. Eastern Time.

"I was just informed that we got double the number of votes that has ever been received in the great state of South Carolina," he added.

CNN showed Trump leading Haley 59.7% to 39.7% after counting 50% of the votes.

Prior to Saturday's Republican primary election, polls were already predicting Trump would secure a victory in South Carolina.

The loss is a significant blow to Haley’s campaign considering it is her home state where she served as governor from 2011 to 2017.

Haley made it clear Saturday that despite losing the South Carolina primary, she will not suspend her campaign.

"I said earlier this week that no matter what happens in South Carolina, I would continue to run for president. I’m a woman of my word," said the only woman to have entered the Republican contest to her supporters following her loss.

She will now concentrate on campaigning for Super Tuesday on March 5, when voters in 15 US states head to the polls to vote in their state primaries.

Haley has repeatedly questioned the 77-year-old former president's mental fitness and warned another Trump presidency would bring "chaos", but her efforts appeared to do little to damage his standing among Republicans.

Trump has already secured wins in the states of Iowa, Nevada, New Hampshire and the US Virgin Islands.

Read more: Haley slams Trump's remarks on Black voters as 'disgusting'