Speculation was swirling in Washington about whether the murder of a young Democratic Party worker could be linked to last month's leaking of internal party emails.

Seth Rich, 27, was shot twice in the head in what appeared to be an attempted robbery near his home in a suburb of the US capital on July 10, but his belongings were not taken.

Two weeks later WikiLeaks, the website, published thousands of embarrassing internal emails which showed Democratic Party officials favouring Hillary Clinton over her rival Bernie Sanders.

The scandal led to the resignation of the party chairwoman Debbie Wasserman Schultz.

What began as a conspiracy theory on the internet was pushed into the limelight this week when WikiLeaks put up a $20,000 reward for information leading to the conviction of Mr Rich's killer.

Julian Assange, the WikiLeaks founder, then appeared on Dutch television where he refused to confirm or deny that Mr Rich was a source.