Updated

Nigerian security forces and the radical Islamist Boko Haram sect likely committed crimes against humanity in their fighting across the country's Muslim north, both torturing and killing civilians as bloodshed in the region grows, according to a report released Thursday.

The Human Rights Watch report comes just days after soldiers angered by the killing of an officer shot dead more than 30 civilians with machine guns and burned down buildings in a neighborhood in Maiduguri, the spiritual home of Boko Haram.

The report calls on the International Criminal Court to examine the actions of all sides in the conflict and to push for prosecutions of those involved, though it stops short of calling for international proceedings against those involved.

"All parties should respect international human rights standards and halt the downward spiral of violence that terrorizes residents in northern and central Nigeria," states the report.

Boko Haram, whose name means "Western education is sacrilege" in the Hausa language of Nigeria's north, is blamed for killing more than 690 people in drive-by killings and bombings this year alone, according to an Associated Press count. The sect has demanded the release of all its captive members and has called for strict Shariah law to be implemented across the entire country.

The sect has killed both Christians and Muslims in their attacks, as well as soldiers and security forces. Despite leaders enacting martial law and sending more troops into the region, the sect's attacks continue almost unstopped. Recently, the military claimed it killed a number of the sect's senior leaders, as well as put out statements claiming to have killed dozens of other members in its operations.

However, a bombing Monday morning by suspected Boko Haram members, that a soldier said killed a lieutenant, sparked a violent retaliation by the army in Maiduguri, the sect's spiritual home. Troops opened fire with assault rifles and heavy machine guns mounted on armored personnel carriers on a busy street near the local headquarters of the Nigerian Union of Journalists, according to witnesses. Afterward, an AP journalist counted the bodies more than 30 dead civilians and saw more than 50 shops and homes burned.

The military later denied it killed civilians, but offered contradictory explanations about what happened. Activists say they worry that other military strikes against Boko Haram may have killed civilians as well.

The Human Rights Watch report also alleges the military, as well as the police, have used torture and indefinite detentions against the civilian population. One witness who spoke to the group said he saw soldiers torture an inmate at a Maiduguri barracks by "pulling on his genitals with a pair of pliers," while another peeled the skin of a detainee with a razor. The witness said soldiers killed another detainee as he hung from a tree.

The report also claimed the police and military routinely kill and extort civilians. The military denied the allegations, with the report quoting officials as saying that they didn't hold prisoners at the barracks and that "there is no Guantanamo Bay" in Nigeria.

"Despite allegations of widespread security force abuses, the Nigerian authorities have rarely held anyone accountable, thereby denying justice to the victims and further solidifying the culture of impunity for violence in Nigeria," the report reads. "Government officials often issue blanket denials of reports of alleged human rights violations and almost never give a public account, in the communities they are meant to serve, of the measures taken to investigate reports of abuses."

The report also went into details about the violence used by Boko Haram, including killing Christians who refused to convert to Islam. One man recounted how in 2009 a preacher continued to preach while being held by Boko Haram members, saying those held "should not betray Jesus."

"They beat him and then carried him away," the man recounted. "I saw one of them cut the back of his neck with a sword. He didn't die right away but continued to struggle."

The Boko Haram violence at times appears aimed at triggering more ethnic and religious violence in Nigeria, a nation largely split between a predominantly Muslim north and a Christian south. Attacks have targeted churches in central Nigeria, where mass killings have occurred before.

"It is . a strategy by Boko Haram to bring the government to its knees by creating a war situation," a Nigerian journalist said, according to the report.

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Jon Gambrell can be reached at www.twitter.com/jongambrellAP .

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Online:

Human Rights Watch: www.hrw.org