Human rights group, Global Amnesty Watch (GAW), has urged the Federal Government to adopt a total clampdown on fleeing elements of terrorist group, Boko Haram sect.
Mr Tom Lever, GAW's Vice President, Africa Affairs, made the appeal in a statement on Tuesday in Lagos.
Lever said that Boko Haram's latest strikes could be out of frustration in reaction to successes recorded against it by Nigerian troops.
He said that the plea followed the recent murder of Red Cross aid worker and midwife, Saifura Khorsa and threat to harm Leah Sharibu, an abducted schoolgirl, who is still in terrorists' captivity.
"Killing Saifura might have been Boko Haram's desperate measure to keep sowing terror in the hearts of people, but it is one the entire world must make them regret by collectively exerting justice.
"There are other ways the sponsors of this group and its fighters could have expressed their frustration at the serial defeat in the hands of the Nigerian military without harming civilian captives.
"Boko Haram must take seriously the warning that nothing must happen to Leah Sharibu with the other aid workers, Hauwa Mohammed Liman and Alice Loksha.
"This would be crossing a red line that would cause the world to demand the application of the stiffest response yet against whatever is left of the group," Lever said
He advised nations and foreign organisations allegedly supporting Boko Haram to have a change of heart, for the sake of humanity.
According to them, those supporting the terrorists should allow the killing of Saifura Khorsa and the threat to harm other captives to prick their conscience.
"While supporting any measures taken to ensure the safe return of the hostages still in Boko Haram captivity, we urge the Nigerian government to acknowledge that the time for being temperate in blotting out what Boko Haram stands for is over.
"The group has repeatedly shown that it is evil in its undiluted form.
"The Federal Government must therefore, prepare contingent measures to visit the harshest consequences possible on the terrorists, should anything happen to those they are holding," he said.
Lever also cautioned certain individuals and groups that had advocated conciliatory approach to the Boko Haram menace.
He, however, expressed condolences to the family of Saifura Khorsa, the Red Cross and the Federal Government of Nigeria.
Khorsa was kidnapped in March along with two other health workers after an attack on a military facility in the town of Rann in Kala Balge area, Borno. (NAN)