Three student protest leaders have avoided prison for leading the huge pro-democracy street protests in Hong Kong two years ago.

Activists Joshua Wong and Nathan Law were sentenced to community service while Alex Chow received a suspended sentence.

Wong, 19, was the most high-profile leader of the protests that erupted in Hong Kong in late September 2014.

The demonstration was dubbed the "Umbrella Movement" after huge crowds of protests occupied major roads for 11 weeks - and weren't deterred by heavy rain.

The activists were protesting to try and get China's Communist leaders to allow fully democratic elections in 2017.

Hong Kong was transferred to Chinese rule in 1997 under the promise of a "one country, two systems" formula with an eventual aim of free elections not enjoyed on the mainland.

Protests erupted after China indicated it would vet candidates wishing to run for leadership in 2017.

Activists slammed the prosecutions for being politically motivated.

Wong told reporters outside court that he would "still commit civil disobedience through non-violent direct action to show my commitment and persistence to fight for human rights, democracy and freedom in Hong Kong."