MAIDUGURI, Nigeria - Suicide bombers attacked a military base and explosions went off Friday around a northeastern Nigerian city that is under siege from a radical Muslim sect, officials said. One blast went off outside a school where parents had arrived to pick up students.

There was no claim of responsibility but blame immediately fell to the sect known as Boko Haram, which has staged targeted assassinations and bombings around Maiduguri, killing more than 240 people this year alone across Nigeria's Muslim north, according to a count by The Associated Press.

The attacks appear to be the most bold and coordinated ever carried out by Boko Haram, whose name means "Western education is sacrilege."

In August, Boko Haram claimed responsibility for a suicide car bombing at the United Nations headquarters in Nigeria's capital, which killed 24 people and left another 116 wounded. Friday's attacks involved four separate assaults, including one on a high-profile military installation.

Borno state police commissioner Simeon Midenda said one blast detonated around noon outside the El-Kanemi Theological College where parents had gathered. Midenda said others had entered the college grounds to attend Friday prayers at a mosque located on its campus.

Witnesses who spoke to an AP journalist said they saw ambulances carry away at least six wounded people from the site.

A short time later, suicide bombers driving a black SUV attempted to enter a base for the military unit charged with protecting the city from Boko Haram fighters, military spokesman Lt. Col. Hassan Ifijeh Mohammed said.

The SUV couldn't enter the gate and the explosives were detonated outside of the base, which damaged several buildings in the military's compound, Mohammed said. The lieutenant colonel said only a few soldiers suffered "minor injuries" from the attack.

Mohammed said blasts occurred at three other places in Maiduguri besides the base, with no one being killed. However, government officials routinely downplay such attacks in Nigeria over political considerations. Mohammed's claims could not be immediately verified by the AP and the police commissioner declined to say how many people had been wounded.

Immediately after the attack, an AP journalist saw soldiers cordon off one neighbourhood and begin an aggressive search. Earlier this week, the military conducted house-to-house searches of some neighbourhoods to collect weapons and round up suspected members of the sect.

The bombings come ahead of Eid al-Adha, or the feast of sacrifice, when Muslims around the world slaughter sheep and cattle in remembrance of Abraham's near-sacrifice of his son. Police elsewhere in the country had warned of violence ahead of the celebration in Nigeria, a country of more than 160 million largely split between a Christian south and a Muslim north.

Boko Haram apparently has split into three factions: One remains moderate and welcomes an end to the violence, another wants a peace agreement with rewards similar to those offered to a different militant group in 2009. The third faction, though, refuses to negotiate.

This most radical faction is in contact with al Qaeda's North Africa branch and likely Somalia-based terror group al-Shabab, a diplomat said on condition of anonymity per embassy orders.