Former US President Donald Trump has pleaded not guilty in a Washington DC court to conspiring to overturn his 2020 election defeat.

During a short arraignment, he spoke softly to confirm his not-guilty plea, name, age and that he was not under the influence of any substances.

He later told reporters the case was persecution of a political opponent.

It marks the third appearance in four months for the former president as a criminal defendant.

Mr Trump entered through a backdoor of the courthouse in the centre of the nation's capital, just yards from the US Capitol and the scene of the January 6 2021 riot that is central to the prosecution's case.

About 1,000 defendants charged with participating in the storming of Congress have appeared in the same court building.

The former president seemed to exchange glances across the court with Jack Smith, the special counsel leading the investigation.

Mr Trump was seen twiddling his thumbs as he sat waiting for the hearing to begin, and he shook his head as the clerk read out the case number.

The former president had taken a short flight on his private plane, Trump Force One, from his New Jersey residence to Washington DC to attend the hearing.

His not-guilty plea covered the four charges made in this latest indictment:

• conspiracy to defraud the US
• conspiracy to obstruct an official proceeding
• obstruction of an official proceeding
• conspiracy against the rights of citizens

Hours earlier, Mr Trump addressed the arraignment on his Truth Social platform, saying to supporters he had challenged what he said was a "corrupt, rigged and stolen election".

Mr Trump decisively lost the 2020 presidential election, the result of which was subject to weeks of uncertainty and challenges across several US states.

The new allegations laid out early this week in an indictment, or charge sheet, include a count of "conspiracy to impair, obstruct, and defeat the federal government function through dishonesty, fraud and deceit".

Prosecutors told Thursday's hearing the case would benefit from a speedy trial. But Mr Trump's legal team said it would need time to prepare for a just and fair trial.

Magistrate Judge Moxila Upadhyaya told the former president not to communicate about the facts of the case.

He was warned that failure to comply could result in an arrest warrant, revoked release conditions, custody, and contempt of court charges.

Speaking to reporters afterwards before boarding his private plane home to New Jersey, Mr Trump said his arraignment was a "very sad day for America".

Standing alongside his close aide and co-defendant in the separate classified documents case, Walt Nauta, Mr Trump added he was sad to see "the filth and the decay and all of the broken buildings and walls and the graffiti" in Washington.

"This is not the place that I left. It's a very sad thing to see it," he said.

The election case amounted to "a persecution of a political opponent," he said. "This was never supposed to happen in America."

The next hearing will take place on 28 August and is expected to be procedural.

The Republican politician has already been charged in two other cases: with mishandling classified files and falsifying business records to cover up a hush-money payment to a porn star.

Mr Trump now faces five upcoming trials - three in New York, over the hush-money payment, and civil trials over business practices and alleged defamation of a woman who accused him of rape.

The fourth trial will take place in Florida relating to the alleged mishandling of classified documents.

Despite mounting legal cases and costs, Mr Trump remains the frontrunner for the Republican nomination for president next year.

A vocal group of supporters waving Trump campaign flags assembled outside court. Anti-Trump demonstrators were also present.