A man 67-year-old man was executed by firing squad in the US state of South Carolina on Friday, prison officials said.

It was the first execution of its type to be carried out in the US in 15 years.

The man, Brad Sigmon, was shot dead by three volunteer prison employees at 6:08 p.m. (2308 GMT) at the Broad River Correctional Institution in the state capital Columbia, prison spokeswoman Chrysti Shain said.

Sigmon had been convicted of murdering his ex-girlfriend's parents with a baseball bat in 2001 after a plan to kidnap their daughter went wrong.

He had planned to kill his girlfriend and himself after taking her on a romantic weekend.

The Supreme Court rejected his last-minute appeal to avoid the execution and South Carolina Governor Henry McMaster denied his appeal for clemency.

Sigmon chose execution by firing squad over lethal injection and the electric chair. His lawyer Gerald King said he had been forced to make an "abjectly cruel" decision about how he would die.

"Unless he elected lethal injection or the firing squad, he would die in South Carolina's ancient electric chair, which would burn and cook him alive," King said.

"But the alternative is just as monstrous," he said. "If he chose lethal injection, he risked the prolonged death suffered by all three of the men South Carolina has executed since September."

Most executions in the US are carried out by lethal injection. The last firing squad execution was in Utah in 2010. Three other states — Idaho, Mississippi and Oklahoma — also authorize the use of firing squads.

Six people have already been executed in the US this year after 25 were killed last year. Half of all US states have either banned or put a moratorium on executions.

Alabama has gone a step further and recently carried out several executions with nitrogen gas, by which gas is pumped into a mask, causing death by suffocation.

UN experts have denounced the use of gas as cruel and inhumane.

Edited by: Roshni Majumdar