Bernie Sanders vows to stay in Democratic nomination race

Bernie Sanders refused to concede defeat to Hillary Clinton late on Tuesday, vowing to "continue the fight" for the Democratic nomination despite his rival declaring herself the party's flagbearer for the US presidential race.

Sanders appeared to ignore the political writing on the wall, after Clinton surpassed the number of delegates necessary to clinch the party's nomination.

Tuesday was the last major date of the 2016 primary calendar, with six states voting.

The former secretary of state extended her delegate lead with wins in New Jersey, New Mexico and South Dakota.