A federal grand jury in Virginia has indicted former FBI Director James Comey on two charges related to his testimony to Congress.

Mr Comey, who has long drawn President Donald Trump's criticism, is accused of lying to Congress during his September 2020 testimony over whether he authorised the leak of classified information to the media.

The probe is being led by Lindsey Halligan, the US Attorney for the Eastern District of Virginia, who was previously Trump's personal lawyer.

Responding to the indictment on Thursday, Mr Comey spoke in a one-minute video on Instagram to declare himself innocent and said he has "great confidence in the federal judicial system".

Mr Comey's arraignment - where charges are formally read out in front of a defendant in court - has been set on the morning of 9 October in Alexandria, Virginia, at 10 am local time, the BBC's US partner CBS reports.

US Attorney General Pam Bondi said in a statement that the indictment "reflects this Department of Justice's commitment to holding those who abuse positions of power accountable for misleading the American people".

Mr Comey has been charged with one count of making false statements and another of obstruction of justice.

The Justice Department asked the grand jury to consider three charges against Comey, but it could only agree that two of them were backed by enough evidence to be tried in court.

The third count was another charge of making false statements.

A grand jury is a group of citizens set up by a prosecutor to determine whether there is enough evidence for charges to be filed. In legal terms, it determines whether probable cause exists to believe a crime has been committed.

He is the first ex-FBI director to be indicted for a crime, and has maintained that he has not lied under oath.

If found guilty, he could face up to five years in prison.

A lawyer for Mr Comey, Patrick Fitzgerald, issued a short statement saying: "Jim Comey denies the charges filed today in their entirety. We look forward to vindicating him in the courtroom."

In his video statement, Mr Comey said: "My family and I have known for years that there are costs to standing up to Donald Trump."

"We will not live on our knees, and you shouldn't either," he continued. "And, I am innocent. So, let's have a trial."

The charges were filed shortly before the five-year statute of limitations was set to expire on Tuesday.

The case had recently been handed over to a new prosecutor after Erik Seibert, the original US attorney overseeing the case, was fired by the Trump administration. He was replaced by Ms Halligan.

According to charging documents, Mr Comey "did willfully and knowingly make a materially false, fictitious, and fraudulent statement... by falsely stating to a US Senator" that he had not "authorised someone else at the FBI to be an anonymous source in news reports".

Prosecutors say the statement was false, as Mr Comey had directed an unnamed person "to serve as an anonymous source in news reports regarding an FBI investigation concerning" another unnamed person.

Around 30 September 2020, the document states, Mr Comey "did corruptly endeavour to influence, obstruct and impede the due and proper exercise of the power of the inquiry" of the US Senate Judiciary Committee through "false and misleading statements".

The case is considered to be the highest-profile indictment of a public figure during Trump's second term.

Trump recently voiced his frustration that prosecutions of his public critics, such as Mr Comey, Senator Adam Schiff and New York Attorney General Leticia James, are taking so long.

"We can't delay any longer, it's killing our reputation and credibility. They impeached me twice and indicted me (5 times!), OVER NOTHING. JUSTICE MUST BE SERVED, NOW!!!" Trump said on Truth Social last week.

After charges were filed, Trump called Mr Comey "one of the worst human beings this Country has ever been exposed to".

"He has been so bad for our Country, for so long, and is now at the beginning of being held responsible for his crimes against our Nation. MAKE AMERICA GREAT AGAIN!"

Asked about Mr Comey hours before the indictment was unsealed, Trump called him a "bad person" but said he had no advanced knowledge of his prosecution.

Laurie Levenson, a former federal prosecutor and a law professor at Loyola Marymount University, said it will be a very challenging case to prosecute.

"It's often the defendant's word against someone else's, and you're gonna have to look at the credibility of both," she told BBC News.

"And even if James Comey got things wrong, that doesn't mean that he knowingly or intentionally lied to Congress. So proving that is going to be the heart of the case."

Ms Levenson also said this prosecution and Trump's public pressure to move forward on it suggest that the traditional firewall between the White House and the US Department of Justice has "collapsed with this case".

Mr Comey served as the FBI's director between 2013 and 2017.

He had a tumultuous tenure that included overseeing the high-profile inquiry into Democratic candidate Hillary Clinton's email just weeks before the 2016 election, which she lost to Trump.

He was fired by Trump amid an investigation into Russian interference in the 2016 election.

This is not the first investigation into the former FBI boss to be launched this year.

He was investigated by the Secret Service after he shared and then deleted a social media post of seashells spelling the numbers "8647", which Republicans alleged was an incitement to violence against US President Donald Trump.

The number 86 is a slang term whose definitions include "to reject" or "to get rid of", according to the Merriam-Webster dictionary, which also notes that it has more recently been used as a term meaning "to kill". And Trump is the 47th US president.

In July, Mr Comey's daughter, Maurene Comey, was fired from her role as a federal prosecutor in the Southern District of New York.

According to media reports, she was given no reason for being removed from the office where she had worked for 10 years.

Earlier this month, she sued the Trump administration over her dismissal.

The Justice Department has been firing lawyers who worked on cases that angered the president, including a special prosecutor investigation of Trump.