Presumptive Republican presidential candidate Donald Trump has been wounded in the right ear in an assassination bid by a gunman at a campaign rally in Pennsylvania, drawing condemnation from world leaders.

The 78-year-old former president was rushed off stage, with blood streaked across his face after the shooting in Butler County on Saturday while the suspected shooter and a rally attendee were killed and two spectators critically injured.

Trump raised a defiant fist to the crowd as he was bundled away to safety, and said afterwards: “I was shot with a bullet that pierced the upper part of my right ear.”

The Federal Bureau of Investigation (FBI) confirmed in a news conference that the shooting was being treated as “an assassination attempt”.

It identified 20-year-old Thomas Matthew Crooks as the “subject involved” in the assassination attempt, the FBI said in a statement on Sunday.

The US Secret Service said in a statement that the suspect “fired multiple shots toward the stage from an elevated position outside the rally” before being “neutralised” by agents.

Police confirmed that a spectator was killed and two critically injured, all of them male adults.

US President Joe Biden said “everybody must condemn” the suspected assassination attempt against Trump. “We cannot allow this to be happening,” Biden said. “The idea that there’s violence in America like this is just unheard of.”

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

Trump’s campaign said he would still attend the Republican National Convention in Milwaukee after he was reported to have had a precautionary hospital checkup.