Donald Trump rushed off stage after shots fired at campaign rally in ...

Donald Trump has been rushed off stage with blood on his face and at least two people, including a suspected gunman, have been killed at a political rally in the United States.

Screams tore through the crowd and Mr Trump, who was speaking on stage, grabbed at the side of his face as gunshots rang out at the rally in Pennsylvania. 

Mr Trump quickly ducked behind the riser as agents from his protective detail rushed the stage. The bangs continued as agents tended to him on stage.

Images showed blood on Mr Trump's face and ear.

Secret Service agents rush Donald Trump off the stage.(AP: Evan Vucci)

The local county district attorney, Richard Goldinger, told AP that the suspected gunman was dead and at least one rally attendee was killed.

Mr Trump raised a fist as he was escorted to a vehicle by the Secret Service, and the crowd began to chant "USA, USA".

Follow the developments after the rally shooting in our live blog

A statement from the Trump campaign said he was "fine".

"President Trump thanks law enforcement and first responders for their quick action during this heinous act," campaign spokesman Steven Cheung said in the statement. 

"He is fine and is being checked out at a local medical facility. 

"More details will follow."

Donald Trump is surrounded by security at the campaign rally.(AP)

US President Joe Biden said he had been briefed.

"I’m grateful to hear that he’s safe and doing well," Mr Biden said in a statement.

"I’m praying for him and his family and for all those who were at the rally, as we await further information.

"Jill and I are grateful to the Secret Service for getting him to safety. 

"There’s no place for this kind of violence in America. We must unite as one nation to condemn it."

Police began vacating the area shortly after Mr Trump left the stage. Some attendees were in tears.

Corey Cumisckey, who was at the event with his wife and children, told the ABC nothing seemed out of the ordinary before the shots were heard.

"Trump was talking and all of a sudden some shots rang out, or what sounded like shots, and then there was some return fire," he said.

"I kind of got up to see what was going on. And they had the president on the ground. And then, you know, a couple of seconds possibly later, they came up with him and off the stage he went."

Mr Cumisckey said his wife was "extremely upset" and questioned whether her children should have been at the event.

"I disagree. I think you should be able to bring your kids to an event like this and it's unacceptable for something like this to happen," he said. 

"It's really unfortunate that things have heated up to this level."

Donald Trump grabs his ear on stage after shots were heard at a rally. 

Mr Trump is due to be endorsed as the Republicans' presidential candidate at the party's national convention in Milwaukee, which begins on Monday. The rally, in Butler in western Pennsylvania, was his last scheduled rally before the event.

Australia's ambassador to the US, Kevin Rudd, said it was a relief Mr Trump was safe, and his thoughts were with the former president and his family.

"All Australians are shocked by the attack on former president Trump at his campaign rally this evening in Pennsylvania," he said. 

"Violence has no place in our democracies."

Republican House Speaker Mike Johnson posted on social media that he was praying for Trump.

ABC/wires