LUCASVILLE, Ohio (AP) - A man convicted of killing a 6-month-old girl while raping her has been executed despite his arguments that he never meant to hurt her.

Steve Smith was executed at 10.29am (10.29pm Singapore time) on Wednesday by lethal injection at the Ohio state prison in Lucasville after his pleas for mercy were denied.

The 46-year-old was convicted of aggravated murder in the September 1998 killing of his live-in girlfriend's daughter, Autumn Carter.

Smith had tried to get his sentence reduced to life in prison, arguing that he was too drunk to realise his assault was killing Autumn and that he did not mean to hurt her.

The Ohio Parole Board and Governor John Kasich rejected his pleas.

Smith became the 51st inmate put to death in Ohio since it resumed executions in 1999.