WASHINGTON: Republican frontrunner Donald Trump on Thursday unveiled an online advert for his presidential election campaign and this one uses footage of Hillary Clinton barking like a dog, suggesting she's unfit to be president.

The ad on Trump's official Instagram account begins with footage of Russian President Vladimir Putin engaged in martial arts and a man who appears to be a militant Islamic State (IS) fighter pointing a gun at the camera.

"When it comes to facing our toughest opponents," it reads, "The democrats have the perfect answer..."

The ad then cuts to footage of Clinton in Nevada earlier this year, barking to mimic an ad she'd been describing to supporters.

It ends with footage of Putin laughing and the words: "We don't need to be a punchline!"

Clinton's campaign staff did not immediately respond to a request for comment.

Related: Trump calls Clinton 'liar' for Islamic State recruiting claim

The real estate tycoon, who is funding his own campaign, has dominated the media spotlight since the start of his campaign due to his bombastic and provocative style.

Trump's first televison advertisement too created a lot of controversy as it demanded a ban on Muslims entering the US while vowing to decapitate the militant Islamic State (IS) group.

“The politicians can pretend it’s something else but Donald Trump calls it radical Islamic terrorism — that’s why he’s calling for a temporary shutdown of Muslims entering the United States,” said the voiceover on the ad.