Donald Trump has stepped up his rhetoric against Barack Obama, accusing the US president of founding the Islamic State.

The Republican candidate’s remarks at a Wednesday night rally came a day after he appeared to hint at gun supporters taking up arms against rival Hillary Clinton.

“Isis [is] honouring President Obama,” he told supporters at the Florida event.

“He is the founder of Isis. He is the founder of Isis, OK?

“He’s the founder. He founded Isis. And I would say the co-founder would be crooked Hillary Clinton.”

Mr Trump also referred to the president by his full name: Barack Hussein Obama.

The remarks were in the same vein as his recent criticism of the Obama administration’s handling of Isis.

He has already previously accused Mrs Clinton of setting up the terrorist group.

Mr Trump’s speech came just hours after the Clinton campaign accused him of casually inciting violence for implying that gun rights advocates could stop her reaching the White House.

The Republican nominee was speaking about the next president's power to appoint Supreme Court justices, a key election issue since the death of conservative Justice Antonin Scalia earlier this year, who has not yet been replaced.

He told a North Carolina rally on Tuesday: "If (Mrs Clinton) gets to pick her judges, nothing you can do, folks.

Then he added: "Although the Second Amendment people - maybe there is, I don't know."