MAIDUGURI, Nigeria - A radical Islamist sect unleashed multiple attacks in northeastern Nigeria, killing at least 25 people, authorities said Tuesday as fears swelled about the government’s inability to corral rising sectarian violence.

The attacks worsened an already tense security situation in Nigeria, a West African nation of more than 160 million people almost evenly divided between Muslims and Christians.

The Boko Haram sect began its attacks Monday evening with blasts targeting police and military targets in the city of Damaturu, authorities said. Gunfire echoed across the city for hours, spilling into Tuesday afternoon. One resident said at least two schools were torched.

The attacks killed at least 20 civilians and five security officers and injured nine other people, according to a Nigerian Red Cross official, Andronicus Adeyemo.

“The terrorists are trying to show that they can’t be stopped,’’ said Yobe State Police Chief Patrick Egbuniwe, who said the dead included three police officers and two soldiers.

The Islamist Boko Haram sect, whose name means “Western education is sacrilege’’ in the Hausa language, is waging an increasingly bloody fight with Nigeria’s security agencies and public. More than 580 people have been killed in violence blamed on the sect this year alone, according to an Associated Press count.

The Yobe State government imposed a 24-hour curfew in Damaturu on Tuesday in an effort to limit casualties. Damaturu had already been under a dusk-to-dawn curfew since a state of emergency was declared in December.