Former US President and Republican nominee Donald Trump’s security was heightened days ahead of the assassination attempt on him during a rally following an Iranian threat. According to media reports, the US Secret Service boosted Trump’s protection after they learned of an attempt by Iran to kill him. The protection, however, seemed unrelated to Saturday's attack. 


US authorities received intelligence from a "human source" on a plan by Tehran targeting the former US president, causing protection to be boosted for Trump, news agency AFP reported, citing CNN. 


In Saturday’s attack on Trump, gunman Thomas Matthew Crooks opened fire at him, leaving the Republican wounded and killing a rally attendee, they said.


As Iran sought revenge for the 2020 killing of Revolutionary Guards commander Qasem Soleimani, the US National Security Council said it had been "tracking Iranian threats against former Trump administration officials for years," as quoted by AFP. "We consider this a national and homeland security matter of the highest priority," spokeswoman Adrienne Watson said in a statement.


The investigation into the shooting incident that occurred on Saturday "has not identified ties between the shooter and any accomplice or co-conspirator, foreign or domestic," she further stated.


Watson referred questions on "additional measures that have been implemented in recent weeks" to the Secret Service and Department of Homeland Security.


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Top Secret Service spokesman Anthony Guglielmi said they and other agencies were "constantly receiving new potential threat information and taking action to adjust resources as needed."


"We cannot comment on any specific threat stream other than to say that the Secret Service takes threats seriously and responds accordingly," Guglielmi added in a statement.


There was no immediate comment from the Department of Homeland Security. The Secret Service has been facing intense scrutiny over the Butler shooting, which raised questions as to how a gunman was able to open fire at the former US President from an exposed rooftop some 150 metres (500 feet) away.


US President Joe Biden has ordered an independent review of the agency's handling of the incident.