Image copyright Reuters Image caption Mr Graham has been highly critical of Mr Trump's campaign

US presidential candidate Donald Trump has given out the mobile phone number of Senator Lindsey Graham - one of his Republican rivals for the White House.

At a campaign rally, he called the South Carolina senator an "idiot" and then told the crowd to try the number.

A Politico reporter called the number on Tuesday, and Mr Graham answered.

Mr Graham recently called Mr Trump "a jackass" and condemned the real estate mogul's comments about Senator John McCain.

Mr Trump has come under increasing criticism from fellow Republicans and veterans groups after he appeared to disparage Mr McCain's war record.

"He's a war hero because he was captured. I like people who weren't captured," he said, referring to Mr McCain's time as a prisoner of war in Vietnam.

Recent national polls show Mr Trump with a double-digit lead over his closest Republican rival.

Image copyright Getty Images Image caption Senator McCain and Senator Graham are long time friends and political allies

However the polling was mostly conducted before the controversial comments about Mr McCain.

His rivals are becoming increasingly frustrated as Mr Trump continues to dominate the media coverage of the crowded Republican race.

Mr Trump has drawn headlines since he called undocumented Mexican immigrants "rapists" and "criminals" when he launched his campaign in June.

"The world is literally falling apart… and all we're talking about is Donald Trump," Mr Graham told CNN on Monday.

Analysis - Nick Bryant, BBC News, New York

To question the military record of Senator John McCain, a former prisoner of war tortured so brutally that he is unable still to raise his arms above his shoulders, would ordinarily have been suicidal.

But Trump is operating under rules of his own making that are perfectly suited to the voracious metabolism of the modern media, and the hyperventilated style of modern campaigning.

The more outrageous his remarks, the more coverage and social media comment he generates. And the more coverage he receives, the better his polling numbers seemingly become.

Increasingly, notoriety equals popularity amongst a large cohort of Republican voters.

Trump: Master of the demolition derby