"Dastardly, inhuman and ungodly," Nigeria says as Boko Haram executes nurse

Nigeria's Minister of Information and Culture, Alhaji Lai Mohammed, described the killing as "dastardly, inhuman and ungodly, saying nothing can justify the shedding of the blood of innocent people."

Hauwa Mohammed Liman was kidnapped alongside two International Red Cross Society (ICRC) aid workers seized by a faction of Boko Haram in March this year during an attack on a military facility.

She was working in a hospital supported by ICRC in a displacement camp in the remote town of Rann outside Maiduguri in Borno State.

One of them, Saifura Hussaini Khorsa, 25, was executed last month by the militants.

'Our daughter is facing a death sentence,' parents of Leah Sharibu cry out

The minister said the government had kept all lines of communications open with her abductors, and it had always acted in the "best interests" of the hostages.

''It is very unfortunate that it has come to this," Mohammed said.

"Before and after the deadline issued by her abductors, the Federal Government did everything any responsible government should do to save the aid worker," he said, adding that, the government will continue working to free the remaining hostages.

The International Red Cross told CNN it has yet to independently confirm Liman's death.

"We have not been able to confirm independently Hauwa's death. We are aware of the media reports that our colleague Hauwa has been executed by her captors, at this stage we cannot confirm if this information is true.

"If confirmed, It would be a devastating blow. For the family, Hauwa's friends and colleagues as well as for all the healthcare workers working in northeast Nigeria," Aleksandra Matijevic Mosimann, ICRC spokeswoman in Nigeria told CNN Tuesday.

Mosimman earlier told CNN they received an ultimatum from the militants on September 16 when the group also issued a threat against schoolgirl Leah Sharibu, whose parents confirmed to CNN she was "facing a death sentence."