The Federal Bureau of Investigation (FBI) has obtained a warrant to search a cache of emails belonging to a top aide of Hillary Clinton, the Democratic presidential candidate.

Emails from Huma Abedin are believed to have been found on the laptop of her estranged husband, former congressman Anthony Weiner, a BBC report said.

There are reportedly 650,000 emails to search through, making it unlikely investigators can give a verdict on them before election day.

The FBI believes the emails might be "pertinent" to its previous inquiry into Mrs Clinton's use of a private server when she was secretary of state in the Obama administration, it said.

The case was closed in July without any charges being brought against Mrs Clinton.

Meanwhile, Democratic leader in the US Senate Harry Reid said the head of the FBI may have broken the law by revealing the bureau was investigating emails possibly linked to Clinton.

Reid accused FBI director James Comey of violating an act which bars officials from influencing an election. News of the FBI inquiry comes less than two weeks before the US election.