BAGHDAD — Anti-American Shiite militia leader Muqtada al-Sadr ordered his followers Saturday to defy government orders to surrender their weapons, as U.S. forces struck Shiite extremists near Basra to bolster a faltering Iraqi offensive against gunmen in the city.
Prime Minister Nouri al-Maliki acknowledged he may have miscalculated by failing to foresee the strong backlash that his offensive, which began Tuesday, provoked in areas of Baghdad and other cities where Shiite militias wield power.
Government television said the round-the-clock curfew imposed two days ago on the capital and due to expire Sunday would be extended indefinitely.
Conflicting claims on airstrike
The U.S. military said a warplane strafed snipers in Basra, killing at least 16 suspected militants after Iraqi troops came under heavy fire.
Iraqi police earlier claimed eight civilians, including two women and a child, had been killed in a predawn airstrike in the Hananiyah neighborhood, a known Shiite militia stronghold.
But Maj. Brad Leighton, a U.S. military spokesman, said U.S. and Iraqi special operations forces had identified snipers on several roofs before the strike was ordered.
An AC-130 gunship then opened fire on enemy positions on three roofs.
"Initial reports indicate 16 criminal fighters were killed," he said in an e-mail response to a query by The Associated Press.
The U.S. Embassy tightened its security measures, ordering all staff to use armored vehicles for all travel in the Green Zone and to sleep in hardened buildings until further notice after six days of rocket and mortar attacks that left two Americans dead.
'Decisive and final battle' in Basra
Despite the mounting crisis, al-Maliki, himself a Shiite, vowed to remain in Basra until government forces wrest control from militias, including al-Sadr's Mahdi Army. He called the fight for control of Basra "a decisive and final battle."
British ground troops, who controlled the city until handing it over to the Iraqis last December, also joined the battle for Basra, firing artillery Saturday for the first time in support of Iraqi forces.
Iraqi authorities have given Basra extremists until April 8 to surrender heavy and medium weapons after an initial 72-hour ultimatum to hand them over was widely ignored.
But a defiant al-Sadr called on his followers Saturday to ignore the order, saying that his Mahdi Army would turn in its weapons only to a government that can "get the occupier out of Iraq," referring to the Americans.
The order was made public by Haidar al-Jabiri, a member of the influential political commission of the Sadrist movement.
Residents of Basra contacted by telephone said Mahdi militiamen were manning checkpoints Saturday in their neighborhood strongholds. The sound of intermittent mortar and machine gun fire rang out across the city, as the military headquarters at a downtown hotel came under repeated fire.
Al-Maliki's risky gambit
The fight for Basra is crucial for al-Maliki, who flew to Basra earlier this week and is staking his credibility on gaining control of Iraq's second largest city, which has essentially been held by armed groups for nearly three years.
In a speech Saturday to tribal leaders in Basra, al-Maliki promised to "stand up to these gangs" not only in the south but throughout Iraq.
Iraqi officials and their American partners have long insisted that the crackdown was not directed at al-Sadr's movement but against criminals and renegade factions — some of whom are allegedly tied to Iran.
Al-Maliki told tribal leaders that the offensive in Basra "was only to deal with these gangs" — some of which he said "are worse than al-Qaida."
Without mentioning the Sadrists by name, al-Maliki said he was "surprised to see that party emerge with all the weapons available to it and strike at everything — institutions, people, departments, police stations and the army."
Al-Sadr's followers have accused rival Shiite parties in the national government of trying to crush their movement before provincial elections this fall. The young cleric's lieutenants had warned repeatedly that any move to dislodge them from Basra would provoke bloodshed.
But al-Maliki's comments appeared to reinforce suspicions that his government failed to foresee the backlash, including a sharp upsurge in violence throughout the Shiite south and shelling of the U.S.-controlled Green Zone, the nerve center of the Iraqi leadership and the U.S. mission.
Two American soldiers were killed Saturday when their vehicle was struck by a roadside bomb in mostly Shiite east Baghdad, the U.S. military said.
Defections to militia's side
With the Shiite militiamen defiant, a group of police in the Mahdi Army's Baghdad stronghold of Sadr City abandoned their posts and handed over their weapons to al-Sadr's local office. Police forces in Baghdad are believed heavily influenced or infiltrated by Mahdi militiamen.
"We can't fight our brothers in the Mahdi Army, so we came here to submit our weapons," one policeman said on condition of anonymity for security reasons.
Slideshow: Iraqi clashes He said about 40 policemen had defected to the Mahdi Army. The figure could not be confirmed, but AP Television News footage showed about a dozen uniformed police, their faces covered with masks to shield their identity, being met by Sheik Salman al-Feraiji, al-Sadr's chief representative in Sadr City.
Al-Feraiji greeted each policeman and gave them a copy of the Quran and an olive branch as they handed over their guns and ammunition.
On Saturday, Iraqi officials said they had received a phone call from Tahseen Sheikhly, the high-profile civilian spokesman for the Baghdad security operation, who was seized by gunmen two days earlier from at his home in a Shiite area of the capital.
An Iraqi-owned satellite television station, Sharqiya, broadcast what it said was a tape of the conversation, in which a man identifying himself as Sheikhly said he was being held "with a group of officers" at an unknown location.
"Our release depends on the withdrawal of al-Maliki from Basra and the easing of the military operations against the Sadrists in all provinces," he said. "We appeal to the prime minister and the Iraqi government to work with the Sadrist movement, which represents the popular base of society."
In Basra, U.S. jets dropped two precision-guided bombs at midday Saturday on a suspected militia stronghold at Qarmat Ali north of the city, British military spokesman Maj. Tom Holloway said.
"My understanding was that this was a building that had people who were shooting back at Iraqi ground forces," Holloway said.
Iraq's Health Ministry, which is close to the Sadrist movement, on Saturday reported at least 75 civilians have been killed and at least 500 others injured in a week of clashes and airstrikes in Sadr City and other eastern Baghdad neighborhoods.
The U.S. military sharply disputes the claims, having said that most of those killed were militia members.
The Associated Press contributed to this report.