US voters head to polls for Super Tuesday

Polls begin closing on "Super Tuesday," the biggest day of the year in the US presidential primaries, with Donald Trump expected to cement his hold on the Republican nomination and set up a rematch with President Joe Biden in November.

Super Tuesday typically decides Republican and Democratic primaries in the giant states of California and Texas, as well as more than a dozen other battlegrounds, and can make or break would-be presidents' White House ambitions.