The only woman on Georgia's death row has been executed - the first female execution in the southern US state for seven decades.

Kelly Renee Gissendaner was pronounced dead by injection of pentobarbitone at the state prison in Jackson.

She was convicted of murder over the February 1997 killing of her husband after she conspired with her lover, who stabbed Douglas Gissendaner to death.

The 47-year-old sobbed as she said she loved her children and apologised to Mr Gissendaner's family, saying she hoped they could find some peace and happiness. She also addressed her lawyer, Susan Casey.

"I just want to say God bless you all and I love you, Susan. You let my kids know I went out singing Amazing Grace," Gissendaner said.

As well as Amazing Grace, Gissendaner also appeared to sing another song before taking several deep breaths and then becoming still.

More than 100 people gathered in rainy conditions outside the prison to support her. Among them was Rev Della Bacote, a chaplain at Saint Thomas Hospital in Nashville, who spent several hours with Gissendaner on Tuesday afternoon, talking and praying.

"She was at peace with whatever was to come," Rev Bacote said.

Gissendaner's three children visited her on Monday but were not able to see her on Tuesday because they were giving evidence to the Georgia Board of Pardons and Paroles, Rev Bacote said.