A Mexican national on death row in the US, has been executed despite Mexican authorities pleading for his life to be spared.

Ruben Cardenas was given a lethal injection at the Texas death chamber in Huntsville for the rape and strangling of his 16-year-old cousin more than 20 years ago.

He told investigators he was high on cocaine at the time.

The Cardenas case drew protests from Mexican diplomats, who said Texas prosecutors did not follow due process and did not let Cardenas speak with Mexican consular officials.

U.S. authorities apparently neglected to notify Mexico about the arrest and failed to hold a review required by the United Nations’ international court in The Hague.

Texas executes more criminals than any other U.S. state which has long caused friction with Mexico, which has no death penalty.

It was the 23rd execution this year in the US compared to 20 in 2016 and 28 in 2015.