John Bolton, who served as Donald Trump's national security adviser before becoming a vocal critic of the president, has been criminally indicted on federal charges.

The Department of Justice presented a case to a grand jury in Maryland on Thursday, and they agreed there was enough evidence to indict Bolton, who issued a statement maintaining his innocence.

It comes after FBI agents searched Bolton's home and office in August as part of an investigation into the handling of classified information.

The indictment makes Bolton, 76, the third of the US president's political opponents to face charges in recent weeks. He could face decades in prison.

According to a 26-page indictment filed at a court in Greenbelt, Maryland, on Thursday, Bolton is charged with eight counts of transmission of national defence information (NDI) and 10 counts of unlawful retention of NDI.

Prosecutors accuse him of illegally transmitting top secret information about US national defence using his personal email and other messaging apps.

"These documents revealed intelligence about future attacks, foreign adversaries, and foreign-policy relations," the court papers state.

If found guilty, Bolton could face up to 10 years in prison for each charge. He is expected to surrender to authorities on Friday.

"No one is above the law," US Attorney General Pam Bondi said in a statement announcing the charges.

Bolton said in a statement that he looked forward to defending his "lawful conduct" in court as he accused Trump of seeking "retribution against me".

"Now, I have become the latest target in weaponizing the Justice Department to charge those he [Trump] deems to be his enemies with charges that were declined before or distort the facts," Bolton said.

Bolton's lawyer, Abbe Lowell, said the charges stemmed from diary entries kept by his client over his 45-year career in public service.

"Like many public officials throughout history, Amb Bolton kept diaries – that is not a crime," said Mr Lowell.

He described the records as "unclassified, shared only with his immediate family, and known to the FBI as far back as 2021".

According to CNN, Bolton is alleged to have shared the information with his wife and daughter.

The unauthorised information includes "diary-like entries from Bolton's time as the National Security Advisor" and were allegedly "printed and stored" at Bolton's home in Bethesda, Maryland.

Bolton was fired from Trump's first administration in 2019. His 2020 memoir, The Room Where It Happened, recounted his time working under Trump and portrayed him as a president who was ill-informed about geopolitics.

The White House filed a lawsuit to block the book from being published, arguing it contained classified information and had not been properly vetted. A judge denied the request and the book was released days later.

The US Department of Justice then opened an investigation into whether Bolton had mishandled classified information by disclosing certain information in the book.

Asked about the indictment on Thursday at the White House, Trump said he did not know about it, but added that Bolton was "a bad guy".

Bolton, who served as George W Bush's UN ambassador, was among former officials critical of Trump who had their Secret Service protection stripped in January.

He is the third Trump critic to be criminally charged since September.

New York City Attorney General Letitia James was indicted on bank fraud charges in October.

Former FBI director James Comey was charged in late September with lying to Congress.

The cases were filed after Trump urged the US attorney general to prosecute his political opponents.

"We can't delay any longer, it's killing our reputation and credibility," he wrote on social media. (BBC)