Facebook will send postcards to verify the location and identity of people buying election-related advertising in a bid to curb foreign nationals' ability to influence American politics.

The social network has come under intense scrutiny for the part it played in the 2016 US election, in which Russians paid for political adverts, spread divisive political views and so-called "fake news" in a bid to vilify Hillary Clinton and promote her Democrat rival Bernie Sanders and Republican opponent Donald Trump.

In an attempt to stamp out a repeat incident, Facebook will now send a postcard to anyone looking to buy political advertising that mentions a specific candidate running for federal office. The letter will contains a specific code that will need to be input online, Facebook's global director of policy, Katie Harbath revealed.

"If you run an ad mentioning a candidate, we are going to mail you a postcard and you will have to use that code to prove you are in the United States," Harbath said during the National Association of Secretaries of State conference on Saturday, Reuters reported.

Previously, individuals or organisations simply needed an email address and the necessary fee in return for influence on the website.