Christians have been warned by a militant Islamist group to leave northern Nigeria or be attacked, according to media reports.
Abul Qaqa, a purported spokesman for Boko Haram, said the terror group was “giving a three-day ultimatum to the southerners living in the northern part of Nigeria to move away”, the English language Vanguard newspaper reported.
The group has been linked to many attacks on Christians, most notably the bombings on Christmas Day killed 49 people, most of them at a Catholic church as services were ending.
Nigeria’s 160 million people are divided between the mainly Muslim north and predominately Christian south.
Qaqa said Boko Garam wished "to call on our fellow Muslims to come back to the north".
The BBC reported that Nigeria’s president, Goodluck Jonathan, declared a state of emergency on Saturday in parts of four states hard hit by violence blamed on Boko Haram.
It said Mr Jonathan vowed to "crush" the group, which he said "started as a harmless group" but had "now grown cancerous".
Human rights activist Shehu Sani told CNN that the latest Boko Haram threat was credible, but many Christians born and raised in the north have nowhere else to go.
"The killings will continue," he told CNN, adding that the state of emergency and an enhanced presence of the security forces would not improve the situation, alleging that troops had already been involved in human rights abuses and had done little to reduce violence.
David Cook of Rice University, who has studied the rise of Boko Haram, told CNN that "if radical Muslim violence on a systematic level were to take hold in Nigeria ... it could eventually drive the country into a civil war."