Last updated 8.03am with identification of shooter

Donald Trump was hit in the ear and slightly injured in an apparent assassination attempt by a gunman at a campaign rally Saturday, in a chaotic and shocking incident that fueled tensions ahead of the US presidential election.

The 78-year-old former president was rushed off stage with blood streaked across his face after the shooting in Butler, Pennsylvania, while the gunman and a bystander were killed and two spectators critically injured.

The Republican candidate raised a defiant fist to the crowd as he was bundled away to safety and said afterward "I was shot with a bullet that pierced the upper part of my right ear."

He was seen walking off his plane unaided hours after surviving the shooting in a video posted by his deputy communications director on social media. 

President Joe Biden, who is set to face Trump in November's deeply polarized election, said the incident was "sick" and added that there was "no place in America for this kind of violence."

Biden phones Trump

Biden later spoke to Trump, the White House said, in their first contact since a debate just over two weeks ago in which the president gave a disastrous performance.

As multiple bangs ran out, Trump, wearing a red "Make America Great Again" cap, grimaced and clutched a hand to his ear, with blood visible on his ear and cheek.

He ducked to the floor as Secret Service agents swarmed onto the podium, surrounding him and escorting him roughly off the stage to a nearby vehicle.

"It is incredible that such an act can take place in our Country," Trump said on his Truth Social network within hours, in remarks sure to stoke the political hostility already engulfing the United States.

"I knew immediately that something was wrong in that I heard a whizzing sound, shots, and immediately felt the bullet ripping through the skin," Trump said.

"Much bleeding took place, so I realized then what was happening."

US media said that the shooting was being investigated as an assassination attempt.

The US Secret Service said in a statement that the suspected shooter "fired multiple shots toward the stage from an elevated position outside the rally" before being "neutralized" by agents.

It confirmed the death of a spectator while two others were critically injured. 

Shooter is a 20-year-old man

The shooter was later identified as 20-year-old Thomas Matthew Crooks of Pennsylvania, US media reported early Sunday.

"The FBI has identified Thomas Matthew Crooks, 20, of Bethel Park, Pennsylvania, as the subject involved in the assassination attempt of former President Donald Trump on July 13, in Butler, Pennsylvania," the FBI said in a statement quoted by NBC and CBS.

Unconfirmed images appeared to show the assailant's body lying on the sloping roof of low building from where he had fired.

The attack sent shock waves around the world, with the leaders of Britain, Israel, Japan and a host of other countries expressing outrage. 

Biden cut short a weekend trip to his Delaware beach house to return to Washington. He will receive an updated briefing from security officials on Sunday morning, the White House said.

President Biden condemns the shooting, before speaking to Trump.

The attack has already had a political impact, with some Republicans pointing the finger and right-wing conspiracy theories flooding social media.

Possible Trump vice presidential pick J.D. Vance said Biden's "rhetoric" had "led directly" to the Trump attack. 

The shooting happened at Trump's final campaign rally before the Republican National Convention in Milwaukee next week.

Trump's campaign said he would still attend after he was reported to have had a precautionary hospital checkup.

Screams and panic

But the convention will now be dominated by the shooting at the rally, which descended into panic with screams and shouts ringing out after the gunshots.

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

He turned back to the crowd and repeatedly raised his fist, as well as mouthing words that weren't immediately discernable, in what instantly became an iconic image.

Agents bundled the tycoon into an SUV, as he once more shook his fist.

"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.

US political figures including former presidents Barack Obama and Bill Clinton lined up to condemn the attack and say there was no place for violence in politics.

Billionaire Elon Musk meanwhile reacted by quickly endorsing Trump.

The United States has a history of political violence, and presidents, former presidents and candidates have tight security.

President John F. Kennedy was assassinated in 1963 while riding in his motorcade, and his brother Bobby Kennedy was shot dead in 1968. President Ronald Reagan survived an assassination attempt in 1981.