Three-quarters of Americans felt "positive" about Donald Trump's nomination acceptance speech, according to a snap poll.

The survey by CNN/ORC, carried out just after Mr Trump accepted the Republican party's nomination for US president, found 57 per cent of people were "very positive" and 18 per cent were "somewhat positive" about his remarks, which focussed on his central message of keeping people safe from perceived threats, such as immigration from South America, Islamist terrorism and violent crime.

The remaining quarter said they thought his speech had a "negative effect".

Accepting his party's nomination in the Quicken Loans Arena in Cleveland, Mr Trump said he was "the voice" of the American people, and presented himself as "the law and order candidate" at a "moment of crisis for [the] nation".

Highlighting attacks on police and the threat of terrorism, he said "any politician who does not grasp this danger is not fit to lead our country".

Mr Trump launched a fierce attack on Hillary Clinton, describing her as a puppet being propped up by "big business, elite media and major donors".

"They know she will keep our rigged system in place," he said.

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The Republican candidate's speech was the longest nomination acceptance speech since 1988, stretching to some 75 minutes, according to CNN.

While on stage the billionaire was greeted by cheers and chants of his name, and when he finished speaking a cloud of red, white and blue balloons were released into the crowd.

However, in response, Ms Clinton tweeted: “We can do better than this.”

And Bernie Sanders, her one-time Democratic rival, also wrote in a tweet: “Trump: 'I alone can fix this.' Is this guy running for president or dictator?"

But many Americans showed their support for Mr Trump on Twitter, using the #MakeAmericaGreatAgain hashtag to congratulate him and praise him on his speech.

Barack Obama's acceptance speech in 2008 got a 58 per cent positive review, according to a poll by Gallup, with 35 per cent saying it was "excellent" and 23 per cent "good".