Former vice president Joe Biden Photo: VCG

Former US Vice President Joe Biden was projected to win Tuesday's Democratic primary in the states of Mississippi and Missouri, local media reported.

Black voters were thought to have delivered a decisive victory for Biden in Mississippi, since exit polls found that about two-thirds of Democratic voters in the deep south state are black, the highest rate of any state that has voted so far.

An NBC News exit poll also showed broad support underpins Biden's Missouri victory.