Saudi journalist Jamal Khashoggi, who was murdered in October at his country's Istanbul consulate, has been named Time magazine's "Person of the Year" alongside several other journalists, in a cover story headlined 'The Guardians and the War on Truth'.

The magazine also honoured Philippine journalist Maria Ressa, Reuters reporters Wa Lone and Kyaw Soe Oo - currently imprisoned in Myanmar - and the staff of the Capital Gazette in Annapolis, Maryland, including five members killed in a June shooting.

Time, which has awarded the "Person of the Year" title annually since 1927, published four different magazine covers for this week's edition, each one spotlighting different honourees.

It is the first time someone has been chosen posthumously for the prestigious cover.

US President Donald Trump, the 2016 "Person of the Year," was the bookmakers' favourite this year but in the end was runner-up.

Special Counsel Robert Mueller, investigating possible collusion between Russia and Mr Trump's 2016 election campaign, was ranked third.

Time's annual distinction is intended to recognise the person, group, thing or idea that had the greatest influence on world events that year.

"For taking great risks in pursuit of greater truths, for the imperfect but essential quest for facts that are central to civil discourse, for speaking up and for speaking out, the Guardians - Jamal Khashoggi, the Capital Gazette, Maria Ressa, Wa Lone and Kyaw Soe Oo - are Time's Person of the Year 2018," Time editor-in-chief and CEO Edward Felsenthal said in a statement.

Ms Ressa, a frequent critic of Philippine President Rodrigo Duterte, and her site were charged with tax evasion by the Philippines' justice department in November.

The four groups were highlighted on four separate covers of the magazine, one of which features the wives of the imprisoned Reuters reporters embracing one another as they hold photos of their husbands.