Media playback is unsupported on your device Media caption US presidential candidate: 'What is Aleppo?'

One of the third-party candidates in the US presidential election has been ridiculed after being wrong-footed by a question on a key Syrian battleground.

Asked what he would do about the city of Aleppo, if elected, Libertarian Gary Johnson answered: "What is Aleppo?"

Mr Johnson later admitted he had "blanked" but said he would "get smarter" following the gaffe.

Aleppo has been one of the major flashpoints of Syria's five-year civil war.

Known as "Halab" in Arabic, it is one of world's oldest continually inhabited cities, being mentioned in Egyptian texts from the 20th Century BC.

Fighting in Syria has escalated in recent weeks, with an estimated 250,000 people living in besieged rebel-held areas.

Although he trails far behind Republican Donald Trump and Democrat Hillary Clinton in polls, both main party candidates are said to be unpopular among many US voters and analysts believe Mr Johnson could play a part in deciding the result.

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But he seemed unaware of the crisis in Aleppo when asked for his solution by MSNBC panellist Mike Barnicle, saying: "And what is Aleppo?''

"You're kidding me?" replied Mr Barnicle, before going on to describe the situation there.

Media playback is unsupported on your device Media caption Do Americans know #WhatIsAleppo or who Gary Johnson is?

"OK, got it, got it," said Mr Johnson, before adding: "With regard to Syria, I do think it's a mess. I think that the only way that we deal with Syria is to join hands with Russia to diplomatically bring that at an end."

Russia and the US have largely backed opposing sides in the Syrian conflict, with Russian aircraft providing air support to President Bashar al-Assad's forces.

Mr Johnson later issued a statement saying: "Can I name every city in Syria? No. Should I have identified Aleppo? Yes. Do I understand its significance? Yes," he said.

Social media has been withering in its response, with #WhatisAleppo trending

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Others said the comments raised serious points

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And Mr Johnson did have sympathisers

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