President Goodluck Jonathan of Nigeria has declared a state of emergency in parts of the country after a series of bombings by the Boko Haram group.
The declaration covers parts of Yobe and Borno states in the north-east, Plateau state in central Nigeria and Niger state in the east. International borders in these areas are temporarily closed.
Mr Jonathan vowed to crush Boko Haram, which killed 42 people in bombings of churches and other targets across the country on Christmas Day.
At a church in the capital Abuja where 37 people died, the president said on Saturday that Boko Haram started as a harmless group but had now grown cancerous and wanted to kill the country.
''But nobody will allow them to do that,'' he said.
The BBC reports Mr Jonathan's announcement means parts of Nigeria's borders with Niger, Chad and Cameroon are sealed until further notice.
He also ordered the armed forces set up a new anti-terrorism force.
Boko Haram wants to impose Sharia law across Nigeria.
Meanwhile, rival ethnic groups have fought each other in the south-eastern state of Ebonyi, leaving at least 50 people dead.