Updated

A spokesman for Al Qaeda in Iraq said Friday that a Sunni Muslim war against Shiites in Iraq is inevitable and threatened relentless waves of attacks like the one a day earlier that killed at least 55 people.

The statement by Abu Muhammad al-Adnani, spokesman for the Al Qaeda-linked Islamic State of Iraq, tap into fears in Iraq and abroad about the country's future stability and the government's ability to protect its citizens following the withdrawal of the last U.S. troops in December.

Despite deadly assaults against the Shiite-led government's security forces and Shiite pilgrims, there has been no indication that Iraq is returning to the sectarian bloodshed of 2006 and 2007 that pushed the nation to the brink of civil war. But Iraqis are increasingly frustrated with the government's failure to prevent attacks that continue to kill scores of Iraqis every month.

In the latest attack, a series of bombings and shootings across the country on Thursday killed 55 and wounded more than 225. Al Qaeda in Iraq claimed responsibility for the attacks.

In a 33-minute audio statement posted on an extremist website, al-Adnani warned of an impending "stage of real confrontation and war against the despicable (Shiites)."

"The war of the Sunnis with the (Shiites) is a religious war, a holy war of faith," he said, according to a translation of the remarks provided by the SITE Intelligence Group, which tracks Islamist extremist messages. "There is no way out of it and there is no swerving from it."

His comments played on fears of a new surge in sectarian violence two months after the American military withdrawal from Iraq. Attacks are nowhere as frequent as they were during the tit-for-tat sectarian fighting from 2005 to 2007.

Tensions between Sunni and Shiite Muslims have lingered for centuries since Islam split into the two sects after the death of the Prophet Muhammed in 632. In Iraq, the minority Sunnis have feared being politically sidelined since the overthrow of Saddam's Sunni-led regime.

On Friday, an aide to Iraq's most prominent Shiite cleric, demanded that the government protect its citizens.

"Is there a glimmer of hope that these explosions come to an end in Iraq?" Ahmed al-Safi, an aide to Grand Ayatollah Ali al-Sistani, said during a Friday sermon in the Shiite holy city of Karbala.

"After a few days, when people calm down and forget, these explosions take place again. We live in the whirl of this unsolved security problem. How long will the situation last?"

Claiming responsibility for Thursday's attacks, a separate Islamic State of Iraq statement said it targeted security forces and government officials to avenge what it described as executions and torture of Sunnis in government prisons.

Iraq's Shiite-led government has executed at least 68 prisoners so far this year, a rate that has alarmed human rights groups. Additionally, last fall Prime Minister Nouri al-Maliki, a Shiite, ordered detentions of hundreds of former Saddam Hussein loyalists, most of whom were believed to be Sunni.