Washington DC - President Donald Trump has commented on the FBI home raid of his outspoken critic and former national security adviser John Bolton on Friday.

Trump, asked about the early morning FBI search of Bolton's home, said he was "not a fan" of his former aide but did not know about the raid ahead of time.

"I saw it on television this morning," the president told reporters.

"He's sort of a lowlife," Trump said. "He's a very quiet person, except on television if he can say something bad about Trump."

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An AFP reporter saw Federal Bureau of Investigation agents entering Bolton's home in the Washington suburb of Bethesda early in the morning.

A police car with flashing lights was stationed outside the house, while journalists and onlookers gathered in the leafy street.

According to The New York Times and other media outlets, the search was ordered to determine whether Bolton had illegally shared or possessed classified information.

The Washington Post said Bolton was not at home at the time of the raid and has not been charged with a crime.