Image copyright AP

White House candidate Donald Trump's allies have said he is a "genius" if a report is true that he paid no federal income taxes for 18 years.

The New York Times said it had received some of Mr Trump's 1995 tax documents revealing $915m losses that allowed him to legally avoid paying taxes.

The real estate tycoon's camp refused to confirm or deny the report, but said the filing was "illegally obtained".

The campaign of his rival, Hillary Clinton, called it a "bombshell".

But the Republican presidential nominee's surrogates took to the airwaves on Sunday morning to defend him.

New Jersey Governor Chris Christie said the New York Times article was a "very good story" because it showcased the "genius" of Mr Trump.

Mr Christie told Fox News Sunday the report would only underline that Mr Trump is best qualified to ease tax policy on working people.

Analysis by Anthony Zurcher, BBC North America reporter

There's no evidence at this point that Mr Trump did anything improper. Just because it's legal, however, doesn't mean this revelation isn't potentially damaging. First, Mr Trump has staked his campaign on being a savvy businessman, and posting a financial loss so large that his tax accountant's software couldn't process the number could undermine that claim.

Then there's the fact that Mr Trump has, over the years, condemned prominent Americans,­ including Barack Obama and Washington Post owner Jeff Bezos, for not paying enough taxes. Now he looks like a hypocrite.

Hotel impresario Leona Helmsley once famously said that "only little people pay taxes" - and she was excoriated for it. Americans know the wealthy have a multitude of ways to avoid taxes. Knowing is different from seeing the cold, hard evidence, however. At the very least, this latest revelation once again puts Mr Trump on his heels in the final weeks of the presidential campaign.

Rudy Giuliani, a close adviser to Mr Trump, also said the Republican nominee was an "absolute genius" if he avoided federal income taxes.

"A lot of the people that are poor take advantage of loopholes and pay no taxes," the former New York mayor told NBC's Meet the Press on Sunday.

"Those are loopholes also."

Image copyright AFP Image caption Mrs Clinton raised the tax issue during the first debate

Mr Trump himself played down the report on Sunday. "I know our complex tax laws better than anyone who has ever run for president and am the only one who can fix them. #failing@nytimes," he tweeted.

During the first presidential debate last Monday, Mrs Clinton attacked Mr Trump for not releasing his tax returns, as all previous White House candidates have done since Jimmy Carter in 1976.

The Democratic nominee suggested he was hiding "something terrible" and that he had perhaps not paid any federal income tax. He replied: "That makes me smart."

In its story, the New York Times said three pages of documents were anonymously sent last month to one of its reporters who had written about Mr Trump's finances.

A former accountant for the property tycoon, Jack Mitnick, whose name appears as Mr Trump's tax preparer of the filings, said the documents appeared to be authentic copies of portions of the 1995 returns, according to the newspaper.

Mr Trump's campaign did not directly address the authenticity of the excerpts, but the New York Times said a Trump lawyer had emailed the newspaper arguing that publication of the records was illegal.

The Republican candidate's camp accused the New York Times, which has endorsed the Democratic candidate for president, of being "an extension of the Clinton campaign".

Mr Trump, the campaign added, was a "highly skilled businessman who has a fiduciary responsibility to his business, his family and his employees to pay no more tax than legally required.

Image copyright NBC Image caption Alec Baldwin as Trump and Kate McKinnon as Clinton on Saturday Night Live

"That being said, Mr Trump has paid hundreds of millions of dollars in property taxes, sales and excise taxes, real estate taxes, city taxes, state taxes, employee taxes and federal taxes, along with very substantial charitable contributions."

The Clinton camp said Mr Trump embodied the "rigged system" of an unfair US tax code.

Clinton campaign manager Robby Mook said in a statement: "This bombshell report reveals the colossal nature of Donald Trump's past business failures and just how long he may have avoided paying any federal income taxes whatsoever."

Mrs Clinton has already disclosed nearly 40 years of federal income tax returns, while Mr Trump's running mate, Mike Pence, has made publicly available 10 years of his tax returns.

At a Saturday night rally, Mr Trump appeared to accuse Mrs Clinton of marital infidelity.

"Hillary Clinton's only loyalty is to her financial contributors and to herself," he told thousands gathered in Manheim, Pennsylvania.

"I don't think she's even loyal to Bill if you want to know the truth. Why should she be, right?"

Meanwhile, Alec Baldwin has debuted his impression of Mr Trump on Saturday Night Live, parodying the candidate's pronunciation of China, among other things.

Sporting a blonde wig and a lip-puckering scowl, the actor appeared on the comedy show alongside SNL regular Kate McKinnon as Mrs Clinton, using a walking cane.