Heavily armed gunmen attacked police and military buildings along with a prison holding at least 1,500 inmates in southeastern Nigeria and an untold number of them may have escaped, authorities said Monday. The attacks began around 2 a.m. in the town of Owerri in Imo state and last for about two hours, according to local resident Uche Okafor. Gunmen also assaulted various other government buildings around the same time, authorities said. The coordinated attacks come less than two weeks after another wave of violence in southeastern Nigeria, when at least a dozen security officers were killed during attacks on four police stations, military checkpoints and prison vehicles. There was no immediate claim of responsibility but the Nigeria inspector general of police blamed a paramilitary wing of a secessionist movement active in the region called the Eastern Security Network. Police said the attackers used machine guns, rocket-propelled grenades and improvised explosive devices during the overnight violence. “The attempt by the attackers to gain access to the police armory at the headquarters was totally and appropriately resisted,” the statement said. The Eastern Security Network, or ESN, has said it is fighting for the protection of the Igbo people from foreign armed invaders killing their people.