The Boston Marathon has been cancelled for the first time in its 124-year history as organisers have deemed it unsafe to hold the race amid the coronavirus pandemic.

The event has run annually since 1897 making it the longest-running marathon in the world.

It had initially been postponed from its April 20 date and was set for September 14 but Boston mayor Marty Walsh has now ruled that this cannot happen due to public health fears.

"There's no way to hold the usual race format without bringing large numbers of people into close proximity," he said on Thursday.

The 2019 men’s and women’s races were won by Kenya’s Lawrence Cherono and Ethiopia’s Worknesh Degefa.