Three men were killed “execution-style” in a graveyard in southern California, police have said.

Detectives are investigating whether a cartel or gang carried out the murders at the Perris Valley cemetery to “send a message”.

Jaime Covarrubias Espindola, 50; Jose Maria Aguilar-Espejel, 38; and Rodrigo Aguilar-Espejel, 28, were found near the grave of a man who died in Mexico.

“All three were killed there at the same time,” said Riverside County Sheriff Chad Bianco at a press conference.

“That was a message for something. It’s certainly not the norm.”

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The sheriff said he would not release details of the men’s injuries because of the ongoing investigation.

However, when asked if they had been killed “execution-style”, he replied: ”It certainly seems that way,” he said.

The men, who all lived in the Perris Valley area east of Los Angeles, were found dead on Monday morning.

Witnesses claimed that two of the bodies were lying on top of a grave and one looked like it was wrapped up in a sleeping bag.

Officials did not release details of any relationship between them and the man who was buried in the grave.

Detectives are looking at security camera footage to try and pinpoint how the men travelled to the cemetery.

“This appears to be an isolated incident and there is no perceived threat to the public,” the Riverside Sheriff’s Office said in a statement.