A 1st Armoured Division (1AD) spokesman confirmed Operation Iron Promise had kicked off Wednesday in Baghdad but gave no further details.

The operation groups the 1AD with the 1st Cavalry Division, which will take over duties in Baghdad by April as part of the largest US troop rotation since World War Two.

A senior military officer had actually announced the offensive two weeks ago, describing it as targeting foreign fighters and extremists as the army no longer considers Saddam Hussein's followers their main adversary.

"We've relooked the enemy," the officer told reporters in Baghdad. "The motivation of the enemy is changing from former regime to extremists."

The campaign replaces Operation Iron Grip, which focused on the dwindling cells of fighters loyal to Saddam, the officer said.

Of 14 pro-Saddam guerrilla cells operating in Baghdad since last April, eight have been defeated while the other six have been severely impaired, the officier said.

The officer warned that Islamic extremists and foreign fighters remained the greatest threat and cautioned: "The risk of sensational attack has probably gone up."

On March 2, suicide bombings on a Shiite religious holiday killed at least 170 people and wounded more than 500 in Baghdad and Karbala.

WAR.WIRE