At least four policemen have been killed in two separate attacks by suspected separatists in Imo State, police said Tuesday.
In the first incident on Sunday, gunmen bombed the Isu police station in Imo state, killing two police officers and lightly wounding one, the state's police spokesman Michael Abatam said.
"Armed men suspected to be members of the proscribed Indigenous People of Biafra (IPOB)/Eastern Security Network (ESN)... attacked the station from the rear axis because the station has no perimeter wall, shooting sporadically, threw petrol bombs and improvised explosive devices (IED) that ignited the station," he said in a statement.
He said the police engaged the gunmen in a firefight, forcing them to flee and take refuge in two nearby hotels where 17 of them were arrested.
"Unfortunately, two police officers paid the supreme" price, he said, adding another sustained a "minor bullet injury" to the head.
In the second attack, also on Sunday, an ambush in Anambra state killed two police escorts attached to a senior government official from nearby Enugu state.
"Two police orderlies of Enugu state commissioner for lands, Chidi Aroh, were killed in an ambush," Anambra state police spokesman Tochukwu Ikenga told AFP.
He said the commissioner's convoy was returning to his base when it was attacked.
"The escorts fought gallantly to save the commissioner, who managed to escape with his driver," the spokesman said.
"The two police escorts were killed," he said, adding that police were on the trail of the attackers.
Southeast Nigeria has seen a surge in violence, with more than 130 police and other security personnel killed by gunmen since last year, according to local media tallies.
Authorities have blamed attacks on either the outlawed IPOB movement, which is campaigning for a separate state for the ethnic Igbo people, or its armed wing, known as ESN.
The group has denied responsibility for the violence.
Separatist movements in Nigeria are particularly sensitive, after a 1967 unilateral declaration of an independent Biafra republic by dissident Igbo army officers sparked a 30-month civil war.
More than one million people died, most of them Igbos, from the impact of conflict, hunger and disease.