US President Donald Trump hailed the conservative activist Charlie Kirk as a "great American hero" and "martyr" during a speech to tens of thousands of mourners at a memorial service in Arizona.

Trump was the headline speaker at the packed event on Sunday, which saw top officials from his administration, including Vice-President JD Vance, praise Kirk's political legacy after he was shot dead on 10 September.

Kirk's wife, Erika, delivered a tearful speech at the State Farm Stadium near Phoenix, in which she said she had forgiven her husband's alleged killer.

But the US president broke with her forgiveness message to say he disagreed with Charlie Kirk's view of wanting the best for his opponent.

"I hate my opponent and I don't want the best for them," he said, adding: "I'm sorry, Erika."

It was a contrast to the words spoken by Ms Kirk earlier, who delivered perhaps the most powerful moment of the service.

"My husband, Charlie, he wanted to save young men, just like the one who took his life," she said, adding: "I forgive him because it is what Christ did. The answer to hate is not hate."

Tens of thousands of people queued for hours outside the stadium before the event, with some even camping out the night before to secure their spot. Many wore Make America Great Again (Maga) hats, other Trump-branded items and red, white and blue outfits.

Inside the stadium, the mood and atmosphere resembled a raucous political rally or megachurch service with music beforehand from Christian bands who prompted singalongs and prayer from the crowd of almost 100,000.

The list of speakers included members of Kirk's organisation, Turning Point USA, which focuses on conservative activism on college campuses, well-known figures in the conservative movement, Trump administration officials and those who said they had been shaped by Kirk's work and right-wing Christian worldview.

They stressed the need to continue the 31-year-old's activism and emphasised his deep faith throughout the five-hour service. Kirk, who was debating students at a university in Utah when he was shot dead, was repeatedly described as a martyr and cast as a historic figure for the conservative movement.

Several speakers said they believed his death would further revitalise the conservative moment in America, which is already in a powerful position given Trump's hold of the White House and the Republican control of Congress.

"The day that Charlie died, angels wept, but those tears have been turned into fire in our hearts," said Stephen Miller, the White House deputy chief of staff. "Our enemies cannot comprehend our strength."

At one stage, Elon Musk, who had a bitter and public falling out with Trump earlier this year, sat next to the president and the pair shook hands and chatted. He later posted a picture of them together with the caption: "For Charlie".

Within the stands and on stage at the State Farm Stadium, Kirk was revered as an activist for free speech and a mobiliser of the youth vote for Trump. "Charlie didn't just help, he made the winning difference, I promise you that," White House Chief of Staff Susie Wiles said.

"We wouldn't be here without him," Vice-President JD Vance told the crowd, who at times erupted into an extended chant of "U-S-A, U-S-A".

"We've got it from here," he added, while discussing Kirk's political legacy.

Vance was one of several key figures from the Trump administration who spoke on stage, with others including Secretary of State Marco Rubio, Secretary of War Pete Hegseth and Heath Secretary Robert F Kennedy Jr.

'I forgive him'

They were followed by Kirk's wife, Erika, who was tearful at times as she described her relationship and vowed to continue her husband's work. She was named the new CEO of Turning Point USA after his death.

"I saw the wound that ended his life," she said. "I felt everything he would expect to feel. I felt shock. I felt horror, and a level of heartache that I didn't even know existed.

"These past 10 days after Charlie's assassination, we didn't see violence. We didn't see rioting. We didn't see revolution. Instead, we saw what my husband always prayed he would see in this country, we saw revival," Kirk told the crowd.

She then said she had forgiven her husband's alleged killer, 22-year-old Tyler Robinson. "That man, that young man, I forgive him. I forgive him because it was what Christ did and it is what Charlie would do," Kirk said.

There was a raucous reception when President Trump took the stage after Erika Kirk. He repeatedly praised Charlie Kirk, while at times turning to his usual political talking points including crime in American cities and mocking his predecessor Joe Biden.

"He's a martyr now for America's freedom," Trump said of Kirk. "I know I speak for everyone here today when I say that none of us will ever forget Charlie. And neither now will history."

The president then said he disagreed with Kirk on one thing. "He did not hate his opponents, he wanted the best for them," he said, prompting some laughs. "That's where I disagree with Charlie. I hate my opponents and I don't want what's best for them."

Trump also attacked what he called the "radical left" and blamed the left for violence in the country.

At the end of his address, in which he described Kirk as a "great of his generation", Trump was joined on stage by Erika Kirk and the pair hugged as the crowd applauded.

The deeply partisan event was reflective of how Kirk's death has laid bare the extreme political divisions in America, with many on the right casting blame on the left for stoking political violence.

The Trump administration is seeking a crackdown on what it calls the "radical left", which in turn has prompted accusations of government overreach and claims Kirk's death is being used as a pretext to intrude on civil liberties.

Robinson, who has been charged with Kirk's murder, is facing the death penalty but a motive for the killing is yet to be revealed by officials.

Kirk was 18 when he co-founded Turning Point USA, a student organisation focused on spreading conservative ideas on college campuses.

He would hold debates on campuses and became known for his combative style, inviting students to step up to the microphone and challenge his right-wing Christian worldview in front of a baying audience.

Clips of these exchanges built him a huge following - more than 5m followers on X and 7m on TikTok - that helped him mobilise the youth vote for President Trump.

While he energised young conservatives, his remarks on issues such as race and crime also routinely prompted an angry liberal backlash. He was a strong supporter of gun rights, vehemently opposed abortion, was critical of transgender rights and promoted false claims about Covid-19.(BBC)