Donald Trump visibly delighted in the drama unleashed by his snub of last night’s Republican presidential debate, taunting his rivals and host channel Fox News from a nearby charity event designed to steal their thunder.

The billionaire Republican front runner boycotted the debate in Des Moines, Iowa as part of a simmering feud with the conservative news network and went on to schedule a competing event for military veterans, broadcast at the same time and in the same city.

"When you're treated badly, you have to stick up for your rights," the 69-year-old mogul said as he opened the event, doubling-down on his claim that Fox News - and particularly its anchor Megyn Kelly - has shown bias against him.

"I have to go a step further and say that Fox has been extremely nice in the last number of hours," he added. "They called a few minutes ago. Can you come over? I say, hasn't it already started?" he mused.

"They've been very nice and wanted me to go, and apologised and everything," he said.

"But once this started, it's for our [veterans], there was nothing I could do."

Fox News issued a statement saying its chief, Roger Ailes, had spoken to Trump and "acknowledged his concerns." It added that Mr Trump had offered to appear at the debate upon condition Fox News contribute $5m to his charities, which it refused to do.

Mr Trump had taunted Fox and his rivals before the main debate, saying it would be a "total disaster" with low ratings.

On stage he gloated at the turnout for his dueling charity fundraiser for veterans - pulled together just a few kilometres from the Fox News event in just 24 hours, he claimed.

"Look at all the cameras. This is like the Academy Awards. We're actually told we have more cameras than they do by quite a bit."

"We have thousands of people outside trying to get in."

"For me personally is it a good thing? A bad thing? Will I get more votes? Nobody knows. You're going to like it because we raised over $5 million (for charity) in one day. That's not so bad," he quipped.

Mr Trump's no-show plunged the presidential race into uncharted waters just days before Iowans vote on 1 February, opening the months-long nomination process to pick the Democratic and Republican candidates for the November election.

Adding to the spectacle, rival Mike Huckabee, the former Arkansas governor who is languishing in polls and attended an undercard event before the main debate, joined Trump at his veterans’ event, as did low-polling former Pennsylvania senator Rick Santorum.