Pepper spray flies during Trump protest clash in California

Republican Donald Trump and Democrat Hillary Clinton rolled up wins in Northeastern states on Tuesday in a major show of strength and immediately turned their fire on each other in a possible preview of a general election matchup.

Trump easily defeated rivals John Kasich and Ted Cruz in all five states that held contests, Pennsylvania, Maryland, Connecticut, Rhode Island and Delaware, with his margin of victory rivaling that in his home state of New York a week ago.

Supporters and opponents of Trump clashed in California on Tuesday, and five people, including two little girls, were pepper-sprayed by a demonstrator during the heated confrontation, police said.

No serious injuries and no arrests were reported in the clash as about 50 people confronted each other in the Orange County community.

Clinton, already in control of the Democratic race, defeated challenger Bernie Sanders in Maryland, Delaware, Pennsylvania and Connecticut. Her only loss of the night was to Sanders in Rhode Island.

The two front-runners used their victory rallies to snipe at each other in the kind of back and forth that will take place should they win their party's nominations and face off in the Nov 8 election to succeed President Barack Obama.

"I think she's a flawed candidate and she's going to be easy to beat," Trump said.

Trump criticized Clinton's record as secretary of state and her vote as a US senator from New York in support of the Iraq war. He said her only advantage was as a woman seeking to become the first female US president.

"Frankly if Hillary Clinton were a man, I don't think she'd get 5 percent of the vote," he said.

Clinton, in a victory speech in Philadelphia, took aim at Trump for accusing her of trying to "play the woman card".

"Well if fighting for women's healthcare and paid family leave and equal pay is playing the woman card, then deal me in," she said to cheers.

For the Republicans, the Northeastern battles set the stage for a big contest next week in Indiana. Trump needs a victory to get closer to the 1,237 delegates required to win the nomination.

Of 118 committed delegates available on Tuesday, Trump took 105, raising his total delegates to 950.

Clinton's victories on Tuesday gave her 2,141 delegates, pushing her closer to the 2,383 needed for the nomination.

Speech a test of foreign policy

Donald Trump's highly anticipated foreign policy speech will test whether the Republican presidential front-runner known for his raucous rallies and eyebrow-raising statements can present a more presidential persona.

Trump's campaign said his speech on Wednesday will focus on "several critical foreign policy issues" such as trade, the global economy and national security.

Trump has a lot to prove when it comes to calming foreign leaders and policy professionals. They've been stunned by his often brash policy proclamations, like his vow to bar foreign Muslims from entering the country.