UPDATED 8.11PM Republican Donald Trump swept to victory in five northeastern state primaries today, moving him closer to the Republican presidential nomination.

Trump won in Pennsylvania, Maryland, Connecticut, Rhode Island and Delaware, by comfortable margins. He now has 77 percent of he delegates he needs to win the Republican nomination.

Meanwhile Democratic front-runner Hillary Clinton, already in control of the Democratic race, defeated challenger Bernie Sanders in Maryland, Delaware, Pennsylvania and Connecticut, but conceded Rhode Island to Sanders.

LISTEN ABOVE: US correspondent Steve Merczynski speaks to Larry Williams

Trump's win in Pennsylvania came in the largest state up for grabs on Tuesday, but complicated delegate allocation rules mean that only a small portion of the state's 71 delegates will go outright to the winner of the state vote.

Republican challengers Ted Cruz and John Kasich have been trying to co-ordinate in upcoming contests to prevent Trump from securing the 1237 delegates needed to win the nomination outright at the party convention in July.

Speaking after the vote, Trump said he considers himself the presumptive nominee.

"The best way to beat the system is to have evenings like this, where you get record setting votes, where you get record setting delegates.

"I use the analogy of the boxer, you know, when the boxer knocks out the other boxer you don't have to wait around for a decision, and that's what happened tonight."

Trump then turned his attention to Hillary Clinton, saying she's only doing well in the election because of her gender.

He said if she were a man, he doesn't think she'd get five per cent of the vote.

Both he and Clinton have high unfavourable ratings, and Trump has made clear that he intends to attack the woman he calls "crooked Hillary".