The Federal Bureau of Investigation (FBI) is investigating an alleged assassination attempt on former US President Donald Trump, who is seeking re-election after four years out of the White House.

The apparent assassination attempt took place on Sunday at his golf club in West Palm Beach, Florida.

In fact, shots were heard in the vicinity of the club, and Trump is considered to be in a state of security.

US Secret Service agents, stationed a few meters from where Trump was playing, noticed the barrel of an AK-type rifle poking through the bushes flanking the field, about 400 meters away.

The suspect, identified by the US press as Ryan Wesley Routh, had a calm demeanor and showed little emotion at the time of his arrest, according to the international press.

The person who fired the shots has been arrested and remains in the custody of the authorities investigating the case.

The alleged attack comes just nine weeks after the Republican presidential candidate survived another attempt on his life.