Republican presidential candidate Donald Trump has branded The Boston Globe "stupid" and "worthless" in response to a satirical front page printed by the newspaper which lampoons the notion of a Trump presidency.
The fake front page is dated April 9 2017, and its main story is about Mr Trump calling for deportations.
Another article mentions work being halted on a wall at the Mexican border.
There is also a short item about the backlash Mr Trump received after tweeting a photo of a new dog he named "Madame Peng," after China's first lady Peng Liyuan.
In an editorial, the Globe called the satire "an exercise in taking a man at his word".
Speaking on the campaign trail in Rochester, New York, Mr Trump called it a "totally dishonest story".
Back on the campaign trail, front-runners Hillary Clinton and Mr Trump pushed for big wins on friendlier terrain in the north-east.
Both are attempting to build challenge-proof delegate majorities ahead of their nominating conventions, as they battle resilient rivals.
Both Mr Trump and Mrs Clinton campaigned in New York ahead of its April 19 primary which offers a large trove of delegates who will select the parties' nominees at their national conventions in July.
Mr Trump is seeking to rebound in his home state after a decisive loss to his main rival, the ultraconservative Texas senator Ted Cruz, last Tuesday in Wisconsin.
The billionaire real estate developer remains well short of the 1,237 delegates he needs to clinch the Republican nomination.
His campaign is now focusing on developing a delegate-centred strategy akin to the one that Cruz has pursued for months.
"A more traditional approach is needed and Donald Trump recognises that," Paul Manafort, Mr Trump's new delegate chief, told NBC.
Even so, Mr Trump complained that the system is "corrupt" and "crooked" and said it is unfair that the person who wins the most votes may not be the nominee.
"What they're trying to do is subvert the movement with crooked shenanigans," Mr Trump told a crowd of thousands gathered in a packed airport hangar in Rochester, New York.
"We're supposed to be a democracy," he added.
He went on to warn that, if he is denied the Republican nomination: "You're going to have a big problem, folks, because there are people who don't like what's going on."
Mrs Clinton, who lost Wyoming on Saturday night to Vermont senator Bernie Sanders, is trying to maintain her commanding lead among delegates no matter how many states Sanders wins - or how much "momentum" he claims.
Key to her drive is a victory in New York, which she represented in the US senate. Mr Sanders, who was born in Brooklyn, can claim New York as his home state.
After stops in New York City churches, Mrs Clinton headed to Baltimore for her first campaign rally in Maryland, where she picked up the endorsement of popular local congressman Elijah Cummings.
Maryland, where Mrs Clinton is favoured, holds its primary on April 26 along with Pennsylvania, Rhode Island, Delaware and Connecticut.
Mrs Clinton's campaign is looking for big wins across the north-east, in an effort to gain what they have termed an "all but insurmountable" lead in the delegate race.
"I was honoured to serve as your senator for eight years. I worked hard with so many leaders," Mrs Clinton told parishioners at Greater Allen Cathedral in Jamaica, Queens on Sunday morning.
"I'm now running for president to continue the work we've done all those years."
Mr Sanders, who trails Mrs Clinton by hundreds of delegates, is pointing to statewide wins in seven of the last eight state contests.
But his latest victory in Wyoming did nothing to help him in the delegate chase, as both Mr Sanders and Mrs Clinton got seven delegates.
Mr Sanders noted that the contest has moved from the conservative South - "Not a stronghold for me" - into states like New York, Pennsylvania and California where he expects to do well.
Mrs Clinton has 1,287 delegates based on primaries and caucuses, compared to Mr Sanders' 1,037. When including superdelegates, or party officials who can back any candidate, Clinton has 1,756, or 74% of the number needed to clinch the nomination. Mr Sanders has 1,068.
On the Republican side, Mr Trump continued to try to catch up to Cruz's ground operation, which is months ahead and trying to eat into Trump's home state support in conservative pockets of New York.
Mr Manafort said the Cruz campaign was using a "scorched earth" approach in which "they don't care about the party. If they don't get what they want, they blow it up".
For Ohio Gov. John Kasich, it's about winning enough delegates to keep all candidates from locking up a majority of delegates, thereby forcing a contested convention. And that means sowing doubts about the effect that a Trump or Cruz nomination would have on the party.
He said there is "great concern" not just about how each would represent the Republican Party, but about the prospect of a blowout loss up and down the ticket in November.
"We would lose seats all the way from the statehouse to the courthouse", he said - meaning races all down the ballot.
Mr Trump still has a narrow path to nailing down the Republican nomination by the end of the primaries on June 7, but he has little room for error. He would need to win nearly 60% of all the remaining delegates to clinch the nomination before the convention. So far, he is winning about 45%.