WASHINGTON ― Donald Trump, known for his incendiary rhetoric on the 2016 campaign trail, lobbed his latest verbal grenade Saturday, dismissing the military record of Sen. John McCain, a former prisoner of war.

The flamboyant billionaire businessman, reality TV star and Republican presidential contender said McCain ― a decorated aviator who was tortured in a prison camp for five years ― did not deserve hero status for his Vietnam War service.

“He’s not a war hero,” Trump told a gathering of social conservative activists in the Midwestern state of Iowa.

“He’s a war hero because he was captured. I like people that weren’t captured, okay?”

The 69-year-old has never served in the U.S. military.

He went on to assert that McCain “graduated last in his class” at the U.S. Naval Academy in Annapolis in the late 1950s.

McCain, 78, the 2008 Republican presidential candidate against Democratic rival Barack Obama, was captured during a bombing raid over Vietnam in October 1967.

He did not personally react to Trump’s comments, but his daughter, 30-year-old broadcaster Meghan, expressed outrage.

“I can’t believe what I am reading this morning. Horrified. Disgusted.

There are no words,” she wrote on her Twitter account.

“I have a brother that just returned from Afghanistan a month ago. Glad he can come home to this being said about his father and his service,” she added with irony.

Trump’s remarks triggered immediate political uproar, as other top Republicans defended McCain’s military record ― and in the process tried to cash in on their rival’s faux-pas.

“@SenJohnMcCain is an American hero, period. I‘ll denounce any attack against his service and anyone else who wears the uniform. -SW,” said Wisconsin Gov. Scott Walker, who, like Trump is seeking the Republican presidential nomination.

Mitt Romney, the Republicans’ 2012 presidential candidate, wrote: “The difference between @SenJohnMcCain and @realDonaldTrump: Trump shot himself down. McCain and American veterans are true heroes.”

Going into the weekend, Trump was the frontrunner in a crowded field of 15 candidates for the Republican presidential nomination.

His bold remarks in June about undocumented Mexican immigrants being rapists and drug runners kept the bombastic real estate tycoon at the top of the national news agenda for days.

But it remained to be seen how his McCain comments might undermine his run for the White House, given how Americans as a whole value the men and women of their armed forces far more than their politicians.

Trump attended a New York area military academy during his high school years, but never served in uniform.

Selective Service documents obtained during his 2011 White House bid indicated that he managed to avoid the Vietnam War draft thanks to student and medical deferments.

By his own account, McCain ― the son and grandson of admirals who now chairs the Senate Armed Services Committee ― graduated in 1958 fifth from last in his class of 899 cadets at the U.S. Naval Academy in Annapolis, east of Washington.

On his 23rd bombing mission from an aircraft carrier off Vietnam, McCain was shot down in October 1967 and held as a prisoner of war for more than five years.

He endured torture in captivity, but refused an offer of early release out of solidarity for his fellow POWs.

The latest public opinion polls, for Fox News and USA Today, have seen Trump leading the Republican pack with 18 percent, 1 percentage point ahead of former Florida governor Jeb Bush.

Those numbers have so far ensured him a place at the first televised debates of the U.S. primary season, on Fox News on Aug. 6. (AFP)