Joseph Mifsud, the Maltese academic suspected of being a link between the Trump campaign and Russian officials, has gone to ground, CNN reports.

Mifsud was once a regular on the foreign policy circuit, attending conferences the world over. Now, after being identified as a key figure in the US special counsel investigation into Russian influence over the 2016 US presidential election, Mifsud has vanished.

Last Thursday he disappeared from the private university in Rome where he teaches. Repeated attempts to reach him since have been unsuccessful, though he appears to have read some messages from CNN.

But more details are emerging of the background and contacts of the man who emerged last week as "Foreign Contact 1" in court filings relating to charges brought against former Trump aide George Papadopoulos.

In the US affidavit, Papadopoulos claims that Mifsud told him in April 2016 that the Russians had "thousands of emails" relating to Hillary Clinton.

The full CNN report may be read here