Donald Trump has won the presidential primaries in Connecticut, Maryland and Pennsylvania while Hillary Clinton is top in Maryland, US media project.
The two front-runners in the race for the White House are hoping to cement their leads after voters in five north-eastern states went to the polls.
Mr Trump's rivals have already shifted focus away from the north-east.
Ted Cruz and John Kasich have teamed up to help each other in the Indiana, Oregon and New Mexico primaries.
Mr Trump has condemned their pact as a sign of weakness and desperation. More to follow.