The execution of death row prisoner Richard Glossip in Oklahoma has been halted after the State's governor stepped in.

Mary Fallin has issued a 37-day stay of execution to address legal questions about Oklahoma's execution protocols and the chemicals used for lethal injection.

Richard Glossip - who denies any involvement in the murder of his former boss in 1997 - was due to be given a lethal injection tonight.

Earlier 30 people gathered outside the governor's mansion to protest against it.