MAIDUGURI, Nigeria — Suspected Islamic militants have opened fire on students taking exams at a school in the country's troubled northeast, killing at least nine pupils in the latest violence to wrack the volatile region, witnesses said Tuesday.

Bodies of the children in their school uniforms were brought to the local morgue, according to a hospital official who insisted on anonymity because he was not authorized to release the information to journalists.

Monday's attack at Ansarudeen Private School in Maiduguri marked the second time in days that suspected radical fighters have attacked schools. The military reported that 13 people, including high school students and teachers, were killed Sunday night during a five-hour shootout when extremists attacked a boarding school in Damaturu, the state capital of Yobe state.

A student who survived that attack by hiding under a dormitory bed said dozens of fighters who identified themselves as Boko Haram — which means "Western education is sacrilege" — ordered students to take them to the teachers' quarters, where they opened fire on teachers and students.

The student spoke on condition of anonymity for fear of reprisals. Military spokesman Lt. Eli Lazarus said seven students, two teachers, two soldiers and two militants were killed in the attack and that three soldiers were critically injured. He said several militants also were captured.

In another attack Monday, suspected extremists gunned down a group of fisherman on a river bank in Alau, located 20 kilometers outside Maiduguri. Most of the victims were relatives of people who have been arresting members of a radical Islamic sect known as Boko Haram.

"They said: 'Your children brought this fate upon you; they are busy catching our members and handing them to soldiers to be killed,'" recalled one eyewitness who spoke on condition of anonymity for fear of reprisals. "They then shot them dead, and asked the remaining of us to run for our lives and take the message to the youth vigilante."

Islamic militants have killed more than 1,600 civilians in suicide bombings and other attacks since 2010, according to an AP count. Dozens of civilians also have been killed by soldiers according to human rights groups — a charge the military denies.

Fighters from Boko Haram and breakaway groups had taken control of large tracts of land and some villages and towns when Nigerian President Goodluck Jonathan declared a state of emergency May 14, banned Boko Haram and ordered a joint task force of soldiers and police to break an insurgency that poses the greatest risk in years to stability in Nigeria. Africa's most populous nation of 160 million and the continent's biggest oil producer is divided between the mainly Christian south and predominantly Muslim north.

Last week, Nigeria's military claimed to be in control of the area under emergency, the states of Adamawa, Borno and Yobe covering some 155,000 square kilometers (60,000 square miles) bordering Cameroon, Chad and Niger. Military officials said they have killed and arrested dozens of militants in attacks using fighter jets and helicopter gunships, but they acknowledged many fighters likely fled with heavy weaponry including anti-aircraft guns.

The military has offered amnesty to any fighters who surrender.

In that spirit, officials last week released the wife and children of Boko Haram leader Abubakar Shekau along with seven other wives and an unknown number of children who had been detained without charge for 10 months. Nigerian authorities routinely arrest the wives and children of suspects.

Meanwhile, officials warned Tuesday that Islamic militants have driven 19,000 rice farmers from their land in northeast Nigeria while a military crackdown is preventing thousands more from working their fields, raising fears of imminent food shortages.

Food shortages would add immeasurably to the misery in northeast Nigeria. The area abandoned by farmers is a fertile one in the semi-arid Sahel, a regional bread basket created by the receding waters of Lake Chad.

"We anticipate general hunger this year because all roads linking the cities to the farming hinterlands have been closed down," the agriculture commissioner for Borno state, Usman Zannah, told The Associated Press in an interview Tuesday. "Farmers have been locked out of their farm lands while those in the hinterland cannot come to the city for tractors or laborers to get their farms tilled for the next cropping."

Chad Basin Development Authority director Garba Iliya said last week that 10,000 hectares (24,700 acres) of rice paddies have been abandoned by some 19,000 farmers at the peak of the harvesting season. He said 3,500 hectares (8,650 acres) of wheat ready to harvest also has been lost as farmers fled in terror.

"Only 1,500 hectares (3,700 acres) of wheat have been harvested before the terrorists came to chase the farmers and our workers away," Iliya said.

The U.N. High Commissioner for Refugees reported last week that more than 6,000 Nigerians, mainly women, children and the elderly, have fled to the neighboring country of Niger in recent weeks.