The ICRC said it was devastated by the news. "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.
The terrorist group equally vowed to keep Leah Sharibu, the remaining Dapchi schoolgirl, as "a slave for life", the paper said.
TheCable had reported how Leman was killed on Monday.
"It is painful to note that despite efforts by the Federal Government who opened a negotiation channel immediately and put all possible efforts on table to secure an agreeable bargain for the safe release of the abductees, unfortunately, Mr Speaker, the Boko Haram sect took a frightful path of executing these helpless and selfless voluntary health workers who gave their time on earth for the care and wellness of devastated Boko Haram victims", he added. In late March, Boko Haram freed all the abducted Dapchi girls except for Sharibu because she refused to renounce her Christian faith and convert to Islam.
"It is actually bad news for all of us, for the family, for the humanitarian communities, for the health personnel and for all the women, daughters and mothers of Northern Nigeria and far beyond", she told the BBC.
"This situation is heartbreaking, and our thoughts remain with her family", it added.
Following the death however Mohammed issued a statement, saying: "It is very unfortunate that it has come to this".
"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.
More than 20,000 people have been killed and two million others forced to flee their homes in northeastern Nigeria since Boko Haram launched a campaign in 2009, aimed at forming a breakaway Islamic state.
Nigeria's military and government have repeatedly said they are on the point of defeating Boko Haram and its various factions.
The mass abduction of more than 200 schoolgirls from Chibok, Borno state, in April 2014 brought global attention to the insurgency and was widely condemned. Some 107 girls have since been released or found.