Trump gives an explosive start to Republican presidential debate

The first Republican presidential debate got off to an explosive start with controversial front-runner Donald Trump, launching a no-holds barred attack on his rivals and refusing to rule out an independent run.

The first confrontation between the top ten Republican contenders at the prime time event in Cleveland, Ohio on Thursday, began with the Fox News moderator asking any candidate who would not pledge to support the eventual Republican nominee to raise his hand.

The only hand that went up without a moment's hesitation was that of celebrity real estate mogul Trump.

And he still refused to back down when told that an independent run would almost certainly hand the race over to Democrats and likely to another Clinton.

"I can totally make that pledge. If I'm the nominee, I will pledge I will not run as an independent," he said amid gasps in the audience and angry reactions from his rivals.

"We want to win, and we will win. But I want to win as the Republican. I want to run as the Republican nominee."

"I mean, this is what's wrong. He buys and sells politicians of all stripes. He's already hedging his bet on the Clintons, OK?" said Kentucky Senator Rand Paul.

When a host challenged him on some of his past comments about women, Trump rebuked his critics for being too "politically correct".

"You call women you don't like fat pigs, dogs, slobs and disgusting animals," the host said.

Trump quickly responded: "Only Rosie O'Donnell" -- an American comedian, actress, author, and television personality who has often criticised Trump.

"I've been challenged by so many people and I don't frankly have time for total political correctness," Trump quipped.

On the issue of immigration, Trump claimed full credit for bringing it to the nation's attention.

"If it weren't for me, you wouldn't be even talking about illegal immigration, Chris," Trump said to Fox News host Chris Wallace.

"This was not a subject that was on anyone's mind until I brought it up at my announcement," he said.

Asked how he would run the nation's finances when some of his businesses had gone bankrupt four times, Trump asserted he had simply taken advantage of the country's laws like several other top respected businessmen.

Trump then took a swipe at New Jersey Governor, Chris Christie by pivoting to the financial woes of his state.

"I had the good sense to leave Atlantic City, which by the way, Caesars just went bankrupt," Trump said, then gestured to Christie. "Chris can tell you."

Later in the debate, former Florida Governor Jeb Bush, who is running second in polls, criticised Trump's tone saying his "divisive" language could be detrimental to the Republican Party.

"We're not going to win by doing what Barack Obama and Hillary Clinton do each and every day: dividing the country, saying, creating a grievance kind of environment," he said.

Trump shot back that the threats against America were too urgent for such concerns about "tone".

"When you have people that are cutting Christians' heads off, when you have a world at the border and at so many places that it's medieval times," Trump said, adding "we don't have time for tone - we have to go out and get the job done."