Media playback is unsupported on your device Media caption Mitt Romney has won Nevada's Republican caucuses, early results suggest

Mitt Romney has declared victory in Nevada's Republican caucuses, cementing his frontrunner status in the race to be the party's presidential candidate.

With just over 70% of the votes counted, he had secured 47.6% of the vote - well ahead of his nearest rival Newt Gingrich on 22.6%.

It is Mr Romney's second victory in a week, following his success in Florida.

Mr Gingrich - a former House speaker - has vowed to fight on until the party's convention in August.

"I'm not going to withdraw," he said. "I'm actually pretty happy with where we are, and I think the contrast between Governor Romney and me is going to get wider and wider and clearer and clearer over the next few weeks."

Earlier, Mr Gingrich said he expected Mr Romney to win in Nevada, partly due to the state's high Mormon population. Mr Romney is a Mormon.

Mr Romney won Nevada in his previous bid to be the Republican presidential candidate in 2008.

Strong momentum

The former Massachusetts governor waited until only a fraction of the votes had been counted before declaring himself the run-away winner in Nevada, the BBC's Alastair Leithead reports from Los Angeles.

With 70.4% of precincts reporting, Mr Romney had 47.6%, Mr Gingrich had 22.6%, Texas Representative Ron Paul had 18.6% and former Pennsylvania senator Rick Santorum had 11.1%.

Nevada caucuses results Source: Nevada Republican Party Romney 50% Gingrich 21% Paul 19% Santorum 10% 100% of precincts reporting

In his victory speech, Mr Romney made no comment on his fellow Republican rivals, instead turning his attention to US President Barack Obama.

"This president's misguided policies made these tough times last longer," he said. "America needs a president who can fix the economy because he understands the economy, and I do, and I will."

His win in Nevada follows a convincing victory in Florida last Tuesday, and gives him strong momentum going into next Tuesday's contest for Colorado, Minnesota and Missouri, our correspondent says.

Mr Romney scored a big win in New Hampshire, lost by a handful of votes to Mr Santorum in Iowa and suffered a significant loss to Mr Gingrich in South Carolina.

Mr Paul campaigned the hardest in Nevada and had hoped to win second place, but insisted he would continue in the race; Mr Santorum has now fallen even further behind since his win in Iowa.

Nevada has a population of 2.7m but only its 470,000 registered Republicans were eligible to vote in Saturday's caucuses.

The votes are the latest stage in the state-by-state process of picking a Republican nominee to challenge Democratic President Barack Obama in November's general election.

The Republican candidate will be formally selected by delegates at the party's convention in Tampa, Florida, in August.