Late Show host Stephen Colbert shocked TV audiences with a comic sketch about Donald Trump's reaction to the Orlando nightclub massacre which ended with him drawing a swastika on a chalkboard.

Colbert was reacting to a speech Trump made on Monday in which he blasted President Obama's reaction to the incident at The Pulse gay club in Florida in which Omar Mateen gunned down 49 people before being killed in a shootout with police.

Trump had said: 'We’re led by a man that either is not tough, not smart, or he’s got something else in mind... There is something going on.'

Later Trump said in a radio interview: 'I’ll let people figure out for themselves.'

Colbert said he considered himself one of those 'people' and he strode up to the chalkboard and said he was drawing out a 'Figure-It-Out-Atron' to work out what Trump was getting at.

He wrote the words Muslim, Bad Thing, Not Smart, Radical Islam, Something Going On, Inconceivable, Obama, Trump in a clockwise configuration on the chalkboard.

Then after a short monologue he connected several of the words to create a swastika shape.

The sketch drew a big response from Trump opponents on Twitter.

Stephen Colbert shocked audiences when he drew this swastika to mock Donald Trump's reaction to the weekend's nightclub massacre in Orlando, Florida

The skit was in response to an interview, in which Trump said something was suspicious with President Obama's failure to call the Orlando gunman a radical Muslim. Colbert said he would figure out what was going on on the show, and to get in Trump's mindset, the first thing he did was through out his medication

Then he started drawing lines between the terms Trump used in his Orlando speech. Saying perhaps 'Trump' meant 'Obama' is 'not smart' because he won't use the term 'radical Islam'

Then he started connecting the other words, saying 'Trump says this is "inconceivable" so "something must be going on".....probably that Obama is "Muslim" and that is a "bad thing"'

When he connected the two thoughts, the lines formed a swastika, the offensive symbol of the Nazi movement

Harold Itzkowitz wrote: 'Colbert just basically called Trump a Nazi and an a**hole on CBS, with a swastika and the word a**hole.'

Andrew Hight, a Canadian, tweeted: 'Stephen Colbert just drew a swastika on his show in comparison to Trump. I'm screaming with joy.'

But Pundit16 was not amused: 'Monologue on Trump and was the most ignorant and offensive hit piece I've seen. Is Colbert a paid Dem?'

Last year the Hollywood Reporter carried out a survey which suggested that Republicans had deserted the Late Show since Colbert - known for his acerbic imitation of a Right-wing TV host - took over from David Letterman.

Earlier Trump celebrated his 70th birthday in North Carolina and gave a vicious rebuttal to an afternoon of attacks lodged by Hillary Clinton and the president they both hope to replace.

Some viewers reacted angrily to Colbert's satire. Most of the reaction on Twitter to the sketch was positive but that may be because few Republicans watch the show

A few of the reactions came from Trump supporters, who called for Colbert to be suspended from CBS

Trump blamed 'weak, ineffective people' in President Barack Obama's administration for what he said was an out-of-control immigration problem linked to the weekend's gun massacre in Orlando.

The presumptive Republican nominee told the crowd in Greensboro: 'I watched President Obama today. And he was more angry at me than he was at the shooter.'

'The level of anger – that's the kind of anger he should have for the shooter, and these killers that shouldn't be here.'

Trump said the U.S. had no hope of maintaining homeland security 'if you don't know what the term is, and if you don't discuss what the problem is, and if you can't say the real name.'

He said: 'We have a radical Islamic terrorism problem, folks. We can say we don't. We can pretend like Obama that we don't, where Obama spent a long time talking about it and nobody at the end of that speech understood anything other than, "Boy, does he hate Donald Trump".'

Trump told a crowd of 9,000 in North Carolina on Tuesday that Obama sounded more angry at him than he did at Omar Mateen, who had killed 49 people