Boko Haram kills Red Cross staff member in Nigeria after kidnapping three aid workers

Isil-allied Boko Haram jihadists have killed another kidnapped female aid worker in northeast Nigeria, the government said, a month after one of her colleagues was murdered.

Three female health workers were kidnapped during a Boko Haram raid on the remote town of Rann, in Borno state, on March 1 that killed three other aid workers and eight Nigerian soldiers.

Two of the kidnapped women, Hauwa Liman and Saifura Khorsa, worked for the International Committee of the Red Cross (ICRC), while the third, Alice Loksha, worked for the UN children's agency, UNICEF.

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 Boko Haram faction Islamic State West Africa Province (ISWAP).

ISWAP then threatened to kill Liman and Loksha, as well as a 15-year-old Christian schoolgirl Leah Sharibu who was kidnapped from the town of Dapchi, in Yobe state, in February.

The ICRC last weekend appealed for the captives' release and for the jihadists to show mercy, as they were "doing nothing but helping communities" in the conflict-riven region.

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".

He did not initially identify the victim but later added in a tweet that he "commiserated with the family of Hauwa Liman".

The ICRC said it did not have official confirmation, adding: "We desperately hope not. We will provide an update when we have accurate information.

"This situation is heartbreaking, and our thoughts remain with her family," it added.

More than 27,000 people have been killed in northeast Nigeria since the Boko Haram insurgency began in 2009, while nearly two million others remain homeless.

Nigeria's military and government maintain the Islamist rebels are weakened to the point of defeat but fighters have conducted repeated raids on military bases in recent months.

Analysts tracing the conflict believe the switch from attacking "hard" government and military targets to killing hostages is the result of a hardline takeover of the group.

Boko Haram has used kidnapping as a weapon of war during the conflict, abducting thousands of women and girls, and forcing young men and boys to fight in their ranks.

The mass abduction of more than 200 schoolgirls from the Borno state town of Chibok in April 2014 brought global attention to the insurgency and was widely condemned. Some 107 girls have since been released or found.