After former US President Donald Trump received injuries on his right ear during a Saturday election campaign rally at Pennsylvania's Butler, in what is seen as an assassination bid that left the 78-year-old Republican presidential candidate's face streaked with blood, his daughter Ivanka Trump conveyed gratitude for the outpouring of support and concern following the violent incident.

"Thank you for your love and prayers for my father and for the other victims of today's senseless violence in Butler, Pennsylvania. I am grateful to the Secret Service and all the other law enforcement officers for their quick and decisive actions today. I continue to pray for our country,  she wrote, adding a message for his father: "I love you Dad, today and always."

The shooter, along with one bystander who was there to attend the rally died.

As gunshots were heard, Trump, who was just six minutes into his election speech, was seen clutching a hand to his right ear, where blood was visible across his cheek and mouth.

Two other spectators were injured, the Secret Service said in a statement. The incident was being investigated as an assassination attempt.

Secret Service agents were quick to respond and surrounded Trump while escorting him off the stage, as he raised a fist to the crowd in defiance.

Law enforcement agents are investigating the case as a genuine attempt on Donald Trump’s life, the FBI confirmed to the media.

In his first reaction after the shooting at his rally, the 78-year-old Republican presidential candidate said in a statement he "was shot with a bullet that pierced the upper part of my right ear".

"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, who was not seriously injured, said on his Truth Social site.

He is currently doing "fine" and being checked at a medical facility, said reports.