"We are deeply pained by this killing, just like we were by the recent killing of the first aid worker".
In March, she was kidnapped.
But the organisation had decided not to pay a ransom as it would set a risky precedent for the 16,000 aid workers it deploys worldwide, Patricia Danzi, ICRC regional director for Africa, told Reuters.
There had been no news of the trio until last month when the ICRC said it had received footage of Khorsa's killing from the IS-backed Boko Haram faction Islamic State West Africa Province (ISWAP).
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". Most of the other students were freed but the girl, who refused to convert to Islam, remains in captivity.
We are not sure of the exact time or hour when it expires, but are extremely anxious for lives of the Hauwa and Alice.More news: Palm Returns As A Small-Sized Companion Phone
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"Based on our doctrines, it is now lawful for us to do whatever we want to do with them", the group further said.
He also thanked all the friendly governments and the clerics across religious lines, that have continued to work with Nigeria for the safe release of the abducted women.
A second aid worker who was held hostage by Boko Haram for seven months has been executed after a deadline for negotiations expired, the Nigerian government said.
Kidnapped Christian schoolgirl Leah Sharibu will not be executed as threatened by a Nigeria terror group, Nigeria's independent online newspaper, The Cable, reports.
Nigeria's government has not made Boko Haram's demands public, BBC noted, adding, "It is unclear why the ICRC would be targeted when it acted as an intermediary between the government and Boko Haram for the release of the Chibok girls in 2017". "Before and after the deadline issued by her abductors, the federal government did everything any responsible government should do to save the aid worker", the statement read. A midwife working with us in northern Nigeria.
ISWA split from Boko Haram in 2016. They were praised for volunteering to work in a risky area while many others fled or chose to remain in safer communities.