But Nigeria's Information Minister Lai Mohammed announced the latest death as a deadline expired and said the government was "shocked and saddened" at the unjustified killing, calling it "dastardly, inhuman and ungodly".
In an emailed statement on Monday, the Nigerian government confirmed the killing, and reacted to criticism that it had not done enough to save the victims by saying: "the Federal Government did all within its powers to save her life".
He said, "It is very unfortunate that it has come to this".
The executed aid worker, was forced to kneel down, with her hands tied inside a white hijab which has a crest symbol, and then shot at a close range.
"As we have been doing since these young women were abducted, we kept the line of negotiations opens all through". In all the negotiations, we acted in the best interest of the women and the country as a whole.
Liman's killing was done spite of a last-minute passionate appeal by the International Committee of the Red Cross (ICRC) "to the Nigerian Government and to communities and individuals with influence to work toward the release of two committed medical workers abducted in north-eastern Nigeria earlier this year".
The group, while commiserating with the family of the deceased, called on the federal government to ensure the release of Leah Sharibu who has been held hostage by the terrorist group after an attack launched in Dapchi, Yobe State.
Leman, a 24-year-old nurse and student of Health Education at the University of Maiduguri, was in the group that was abducted.
The militants said in a video posted online last month that they would kill at least one hostage once a deadline due to elapse on Monday had passed. We have been told in 24 hours they will be executed.
Meanwhile, ISWAP has threatened to keep Leah Sharibu as a slave.
A schoolgirl who is also being held was among 110 girls kidnapped from a school in the town of Dapchi in February. There has been a global plea for her release.
"We don't have any evidence that they won't keep committing such atrocities, so we have to assume based on their track record, based on what they have done in the past that our Chibok girls, Leah Sharibu, as well as Alice Loksha of UNICEF, who are still in captivity, who are facing similar threats, we can't expect that the terrorists would change their mind and behave differently", he noted. The militants said the teenager would be kept as a slave.
In an audio message sent to one of her male friends when she was captured in March, Hauwa Leman, who spoke in Hausa, said her parents should be informed that she had been kidnapped. They are shooting everywhere.
"As I said on the 18th of September 2018, humanitarian workers, who go into troubled spots to alleviate people's suffering are some of the most courageous and selfless people on the planet".