Former US president Donald Trump was rushed off stage by Secret Service agents Saturday after a series of loud gunshots were heard at the start of a campaign rally in Pennsylvania.

As the bangs ran out, Trump clearly grimaced and clutched a hand to his right ear, on which blood could later be seen.

Agents swarmed onto the podium, surrounded the Republican candidate and escorted him roughly off the stage, as Trump raised a fist to the crowd in a gesture of defiance.

US media reports say two people are dead, including the suspected shooter.

The shocking incident will fuel anxiety in a country already concerned about the prospect of unrest and political harassment in the run-up to the November election battle between Trump and President Joe Biden.

“The former president is safe,” the Secret Service said in a post on X.

His campaign said he was “fine” and being checked at a medical facility.

“President Trump thanks law enforcement and first responders for their quick action during this heinous act. He is fine and is being checked out at a local medical facility. More details will follow,” said spokesman Steven Cheung in a statement.

The incident took place shortly after Trump took the stage at his final campaign rally before the Republican National Convention in Milwaukee next week.

The rally in Butler, Pennsylvania descended into scenes of chaos as bangs were heard and screams and shouts rang out.

“Let me get my shoes,” Trump was heard saying on microphone, as security agents helped him back to his feet.

Agents later bundled the 78-year-old tycoon into an SUV, as he once more raised his fist to the crowd.

“This is an active crime scene,” Secret Service officers told reporters, ordering them out of the area.

‘Horrified’

“We saw a lot of people go down, looking confused. I heard the shots,” said John Yeykal from Franklin, Pennsylvania, who was attending his first Trump rally.

Biden has received an initial briefing on the incident, the White House said.

He was briefed by the head of the Secret Service and the Secretary of Homeland Security, it said.

US politicians reacted with shock to the incident.

Democratic Senate Majority Leader Chuck Schumer said he was “horrified by what happened at the Trump rally in Pennsylvania and relieved that former President Trump is safe.”

“Political violence has no place in our country,” he added.

Republican minority leader Mitch McConnell added: “Tonight, all Americans are grateful that President Trump appears to be fine after a despicable attack on a peaceful rally. Violence has no place in our politics.”