SAN FRANCISCO (REUTERS) - Twitter on Monday (Nov 2) outlined a plan for placing warning labels on tweets from US election candidates and campaigns that claim victory in advance of official results.

The move comes as the social network braces for what it has called an unusual election due to a high number of mail-in ballots that might cause a delay in final results.

Beginning on election night through the inauguration, Twitter said it would place warning labels such as "official sources called this election differently", or "official sources may not have called the race when this was tweeted".

US-based accounts with over 100,000 followers and a significant engagement will also be considered for labelling, Twitter said.

Social media companies are under pressure to combat election-related misinformation and prepare for the possibility of violence or poll place intimidation around the November vote.

In an updated blog, the company said it would consider state election officials and national news outlets such as ABC News, Associated Press, CNN and Fox News that have independent election decision desks as official sources for results.

Their official Twitter accounts will be exempted from labelling, the company said.