US President Donald Trump and his Democratic challenger, Joe Biden last night in Cleveland, Ohio, engaged in a heated verbal  exchange laced for the main part with diatribes in the first presidential debate of the US election.

Trump accused Biden of being a leftist and promoting socialism. Biden openly called Trump a racist and told him to “shut up” as Trump repeatedly tried to goad Biden with interruptions.

Moderator Chris Wallace of Fox News appeared to lose control of the debate and frequently appealed for calm as the two candidates clashed.

The US president was challenged over white supremacist support and refused to condemn a specific far-right group.

In one of the most talked about exchanges of the night, the president was asked by the moderator, Chris Wallace, if he was prepared to condemn white supremacists.

He initially said he would but when asked to denounce the far-right Proud Boys group by name, he sidestepped.

Trump said: “Proud Boys, stand back and stand by, but I’ll tell you what, somebody’s got to do something about Antifa and the left.”

The Proud Boys, an anti-immigrant, all-male group, took to social media to celebrate. “Standing down and standing by sir,” it posted on Telegram.

Trump was asked if he would encourage his supporters to be peaceful if results of the election were unclear. “I’m encouraging my supporters to go into the polls and watch very carefully,” he responded

Opinion polls suggest Mr Biden has a steady single-digit lead over Mr Trump. Polls also suggest one in 10 Americans have yet to make up their mind how to vote.