Riverside County Sheriff Chad Bianco has released details on the third assassination attempt on former US president Donald Trump, saying it was not something they were taking “lightly”.

“We had a very detailed plan in place on how we were going to keep, not only the former president safe, but all of the participants … of the rally safe,” Mr Bianco said during a press conference.

“We had a larger outside perimeter and then an inside perimeter that was completely controlled by us.”