Followers of radical Shiite cleric Muqtada al-Sadr have called for a nationwide civil disobedience campaign to protest raids and detentions.

The head of the Sadrist parliamentary bloc says the move comes because of the continued U.S. and Iraqi actions against the movement's Mahdi Army militia despite a cease-fire. Nassar al-Rubaie has demanded that the raids stop, Sadrist detainees be released and an official apology be issued.

Tuesday's announcement comes as Shiite militia fighters clash with Iraqi security forces in the southern oil capital of Basra. The tensions threaten the cease-fire, which has been critical to an overall decline in violence in Iraq.

AP Television News video showed smoke from explosions rising over the city and Iraqi soldiers exchanging gunfire with militia members.

Meanwhile, the U.S. military said on Tuesday that five suspected militants were killed in Basra while attempting to place a roadside bomb. Ten others were injured after being spotted conducting suspicious activity, the statement said.

Security in the city had been steadily declining in Basra well before the British handed over responsibility to the Iraqis on Dec. 16. But the fierce street fighting was a steep escalation in tensions as rival Shiite factions battle for control of the area.

Al-Sadr's organization has threatened that tensions will escalate in Basra if members of al-Sadr's Shiite Mahdi Army are targeted.

"We are calling for calm, but this new security plan has the wrong timing," Harith al-Edhari, the director of al-Sadr's office in Basra, said Tuesday. "This plan is a government scheme to target the Sadrists as they did in Diwaniyah and Muthanna."

Al-Sadr recently told his followers that although the truce remains in effect, they were free to defend themselves against attacks.

U.S. officials have insisted they are not going after Sadrists who respect the cease-fire but are targeting renegade elements, known as special groups, that the Americans believe have ties to Iran.

At least one Iraqi battalion has already been sent to Basra, an official in the defense ministry said, speaking on condition of anonymity because he wasn't supposed to talk to the media. Other battalions may be called from Iraq's southern provinces.

The clashes follow recent fighting elsewhere in the country between U.S. and Iraqi forces and factions of the Mahdi Army. The Mahdi Army has come under severe strains in recent weeks as the U.S. and Iraqi forces detained followers they accuse of belonging to breakaway groups.

The U.S. military has accused Iran of arming and funding Shiite extremists to fight American forces in Iraq. Iran denies the allegation.