WASHINGTON -- Former US President Donald Trump, the presumptive Republican presidential nominee, on early Sunday urged Americans to stand united and not allow "evil to win," just hours after surviving a suspected assassination attempt at a rally in Butler, Pennsylvania.

"We will FEAR NOT, but instead remain resilient in our Faith and Defiant in the face of Wickedness," Trump said in a post on his social media platform Truth Social.

"In this moment, it is more important than ever that we stand United, and show our True Character as Americans, remaining Strong and Determined, and not allowing Evil to Win," Trump said.

At around 6:12 pm (2212 GMT) on Saturday, Trump was rushed off the stage at the rally by several law enforcement agents after what sounded like gunshots rang out through the crowd.

"A suspected shooter fired multiple shots toward the stage from an elevated position outside of the rally venue," said the US Secret Service in a statement following the incident, adding that agents "neutralized the shooter who is now deceased."

The statement also said that one spectator was killed and two others were critically injured.

Trump said in a post that he was "shot with a bullet that pierced the upper part of my right ear." A statement from his campaign has confirmed the former president is "fine."

The shooting is being investigated as attempted assassination by the FBI, which identified the suspect as 20-year-old Thomas Matthew Crooks of nearby Bethel Park, Pennsylvania.

The gun recovered at the scene was legally purchased by his father, and the suspected shooter had explosive devices in his car, according to US media reports on Sunday morning.

President Joe Biden, in a rare reference to his rival as "Donald," said in a brief remark Saturday night that such action is "sick," and "we cannot allow for this to be happening."

When asked by a reporter about his opinion, Biden said, "I want to make sure we have all facts before I make some comment."