A serial killer who admitted killing six gay men in just eight-months in the US east coast has been executed.

Gary Ray Bowles was given a lethal injection in Florida late Thursday after more than 20 years on death row.

The 57-year-old bludgeoned and suffocated his victims, who were spread from Maryland in the north to Florida in the south, during his grisly 1994 crime spree.

He was nicknamed the I-95 Killer because he appeared to target men living near the interstate highway which spans the eastern seaboard.

In one case, the one-time male prostitute dropped a 40-pound concrete block on the head of Walter Hinton, 47, who had invited him to stay in his Jacksonville trailer. In another, he attacked 38-year-old Albert Morris as they left a bar together in New York state. In all cases, his victims were found with objects stuffed down their throat – including a sex toy, leaves and a towel. In most, they were also robbed.

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It is believed all six – Hinton and Morris, as well as John Hardy Roberts, 59, Milton Bradley, 72, Alverson Carter Junior, 47, and David Jarman, 38 – had been befriended by Bowles before he took their life.

He later told authorities he blamed gay men for his girlfriend leaving him and having an abortion after she found out he had been having sex with males for money.

He was convicted of three murders in 1996 and later admitted another three.

His execution at the state’s death chamber in Raiford came 23 years after he was first placed on death row. A last-minute plea by lawyers claiming Bowles was too intellectually disabled to be executed was rejected by the US Supreme Court.

Before he was put to death, he had a final meal of cheeseburgers, french fries and bacon.

He offered no final words but wrote in a handwritten statement that he regretted what he had done.

“I'm sorry for all the pain and suffering I have caused,” he wrote. “I hope my death eases your pain. I want to tell my mother that I am also sorry for my actions. Having to deal with your son being called a monster is terrible. I'm so very sorry. I never wanted this to be my life. You don't wake up one day and decide to become a serial killer."

Bowles, who originally came from West Virginia, became the 99th inmate to be put to death in Florida since 1976 when the death penalty was restored.