US Republican front runner Donald Trump sealed primary wins in Michigan, Mississippi and Hawaii, brushing off a week of attacks from the party's establishment and expanding his lead in the White House nominations race.
In the Democratic contest, Bernie Sanders stunned front runner Hillary Clinton in a narrow Michigan primary upset, giving his campaign new energy.
Mrs Clinton won in Mississippi, but Mr Sanders' victory is seen as likely to ensure a prolonged fight to pick a candidate for November's general election.
Mr Trump's convincing win in Michigan restored his campaign's momentum and increased the pressure on the party's anti-Trump forces to find a way to stop his march to the nomination ahead of several key contests next week.
He built his victories in Michigan, in the heart of the industrial midwest, and Mississippi in the deep south with broad appeal across many demographics.
He won evangelical Christians, Republicans, independents, those who wanted an outsider and those who said they were angry about how the federal government is working, according to exit polls.
US Republican front-runner Donald Trump has won three more primaries, extending the lead over his rivalshttps://t.co/SSPpCjIwfQ
— RTÉ News (@rtenews) March 9, 2016
At a news conference afterwards, Mr Trump said he was drawing new voters to the Republican Party and the establishment figures who are resisting his campaign should save their money and focus on beating the Democrats in November.
"I hope Republicans will embrace it," Mr Trump said of his campaign. "We have something going that is so good, we should grab each other and unify the party."
The results were a setback for rival John Kasich, governor of Ohio, who had hoped to pull off a surprise win in neighbouring Michigan, and Marco Rubio, a senator from Florida who has become the establishment favourite but lagged badly in both Michigan and Mississippi and appeared unlikely to win delegates in either.
Mr Trump said Mr Rubio's recent attacks on him had backfired.
"Hostility works for some people; it doesn't work for everyone," the real estate magnate said at a news conference in Jupiter, Florida.
Texas senator Ted Cruz, whose recent victories have positioned him as the prime alternative to Mr Trump, won the party's primary in Idaho.
But Mr Trump suggested his rivals had little hope going forward, and took particular aim at Mr Cruz.
"Ted is going to have a hard time," Mr Trump said of his rival. "He rarely beats me."
The Michigan victory sets Mr Trump up for a potentially decisive day of voting next week.
On 15 March, Ohio, Florida, Illinois, Missouri and North Carolina - like Michigan, states rich in the delegates who will select their party's nominee at July's Republican National Convention - cast ballots.
The Republican contests in Florida and Ohio award all the state's delegates to the winner.
If Mr Trump could sweep those two states and pile up delegates elsewhere next week, it could knock Mr Rubio and Mr Kasich out of the race and make it tough for Mr Cruz to catch him.
In the Democratic race, Mr Sanders told reporters in Florida that the results in Michigan were a repudiation of the opinion polls and pundits who had written off his chances in the state.
Polls had shown Mrs Clinton with a double-digit lead going into the primary.
Mr Sanders, a democratic socialist, said the win showed his political revolution was "strong in every part of the country."
'The people's revolution is strong in every part of the country'
— RTÉ News (@rtenews) March 9, 2016
Bernie Sanders reacts to Michigan primary winhttps://t.co/hBXp7mSIJC
