A Republican National Convention delegate puts her fingers in her ears as other delegates scream and yell after the temporary chairman announced that the convention will not hold a roll-call vote on the Republican National Convention Rules Committee's report and rules changes and rejected the efforts of anti-Trump forces to hold such a vote, at the Republican National Convention in Cleveland, Ohio, US July 18, 2016. [Photo/Agencies]

CLEVELAND - The Republican National Convention briefly erupted in chaos on Monday when opponents of presumptive US presidential nominee Donald Trump stormed out of the room and others chanted in a failed attempt to force a vote opposing his candidacy.

The turmoil threatened efforts by the Trump campaign to show the party had united behind the businessman-turned-politician and distracted from the day's theme of "Make America Safe Again," meant to depict Trump as a strong leader capable of shielding the country from violence.

The convention's opening night featured a string of emotional speakers attacking Democratic presidential candidate Hillary Clinton's record as secretary of state under President Barack Obama, arguing she had made Americans vulnerable to Islamist militancy.

The anti-Trump forces interrupted the proceedings earlier in the day, seeking to change the party's nominating rules to allow delegates to support alternative Republican candidates over Trump.

Party leaders held a voice vote, then declared the opponents lacked enough support, triggering pandemonium on the floor of the Cleveland basketball arena where Trump is due to be formally nominated this week for the Nov 8 election.

Many delegates began chanting: "Roll Call. Roll Call," effectively calling for a lengthy process that would allow every state to weigh in. Some, including the Colorado delegation, walked off the convention floor saying they had to assess their next steps.

"This entire system is rigged to force the vote for Donald Trump," said Kendal Unruh, one of the Colorado delegates.

Ken Cuccinelli, a delegate from Virginia who also favored a roll-call vote, called the situation "appalling".

"This is the party of law and order. ... If you won't obey your own rules there is no reason to think you'll obey any others," Cuccinelli, the state's former attorney general, told MSNBC.

Trump's son and adviser, Donald Trump Jr., threatened the leaders of the attempted revolt, saying: "Your careers are finished" in a message posted on Twitter.

While delivering a jolt to the highly scripted program, the anti-Trump forces failed, their rebellion quashed.

The convention then approved the party policy platform and took a scheduled break before a lineup of evening speakers also due to include Trump's wife, Melania, and former New York Mayor Rudy Giuliani.

But the furor, an embarrassment to Trump, put a spotlight on the deep divisions within the party that have emerged over his candidacy. A string of senior Republicans, worried about Trump's temperament and policies, were already avoiding the convention.

Clinton accuses Trump of lacking the experience and temperament needed to work in the Oval Office. On Monday, Clinton, 68, used an address to a largely black audience to cast Trump as someone who would divide the country along racial, ethnic and religious lines.