WASHINGTON (AFP) - A death-row inmate in Texas who confessed to murdering three elderly people with a screwdriver for just US$100 (S$133) was executed on Wednesday, the United States prison authorities said.

Arnold Prieto, 41, was declared dead at 6.31pm local time at the state penitentiary in Huntsville, said Texas Department of Criminal Justice spokesman Jason Clark. Prieto's is the fourth US execution this year.

He was sentenced to death for the triple murder committed during a 1993 robbery when he and two brothers were invited to the siblings' great-aunt and great-uncle's house for breakfast, and attacked the elderly couple.

The 72-year-old man and his 62-year-old wife were killed, along with another 92-year-old woman who was in the house.

Prieto and one of the brothers attacked the three with a screwdriver. Under the influence of cocaine, the trio of friends ransacked the house, stealing jewellry and money.

Splitting cash found in a purse, "we each got about US$100. I also picked out a gold chain, small, like for a child, with a crucifix pendant", Prieto said in his confession.

Several days later, one of the brothers gave him "a couple of earrings and a couple of necklaces" which he pawned for US$140.

In an unusual move, Prieto did not appeal his death sentence to the US Supreme Court.

One accomplice, a minor at the time, was sentenced to life in prison. The second brother was never charged.