vows to overturn execution block

But the first three executions were cancelled because of court rulings.

Hikma, the British manufacturers of the drug, have opposed its use in executions, and the makers of other drugs have tried to halt the executions in the courts, arguing that the prison authorities were unauthorised to use their products.

Midazolam has also been criticised for being ineffective in properly sedating prisoners so they feel no pain when two more drugs paralyse them, and then stop the heart.

But witnesses reported no apparent glitches or signs of suffering from Lee.

Image: Six of the eight men initially due to be executed

JR Davis, a spokesman for the Governor of Arkansas Asa Hutchinson, told reporters: "It is a sombre night all across Arkansas and that this is a responsibility hedoesn't take lightly and it's one of the most grave things he'll ever have to do.

"But in the end, we know the right thing was done tonight. And more importantly, justice for the first time since 1993 for Debra Reese's family."

Ms Reese was beaten to death 24 years ago, but lawyers for Lee said he maintained he was innocent and wanted a delay in execution to allow for fresh DNA testing.

Furonda Brasfield, from the Arkansas Coalition to Abolish the Death Penalty, said she was "dismayed that our governing officials wouldn't allow the innocence claims to be fully explored".

"We could have very well, executed an innocent man tonight, but we will never know that now," she said.

Image: Governor Asa Hutchinson sanctioned the executions

By reactivating the death chamber, Arkansas has