BAGHDAD, Iraq – Fierce fighting raged Tuesday in a Baghdad slum loyal to radical Shiite cleric Muqtada al-Sadr, killing at least 19 people – including one American soldier – and injuring scores more, according to U.S. and Iraqi officials.

Across town, a group of heavily armed gunmen kidnapped two female Italian aid workers and two of their Iraqi colleagues from their office in a brash afternoon raid.

The soldier died in a rocket-propelled grenade attack that injured two of his comrades, according to a U.S. military statement. Fighting in or near Baghdad since Monday afternoon has claimed the lives of six other American troops, bringing the two-day, U.S. death toll to 14.

On a day when U.S. military deaths in Iraq passed 1,000, renewed violence shattered the relative calm that prevailed in the Iraqi capital in recent weeks and threatened to derail a fragile cease-fire brokered between al-Sadr and the interim Iraqi government in the southern holy city of Najaf.

Aides to al-Sadr said the fighting wouldn’t deter them from soon unveiling a political platform based on fundamentalist Islam that would allow his virulently anti-U.S. movement to participate in elections next year.

“We’re the people who fought and confronted him (Saddam),” said the cleric’s Baghdad spokesman, Sheik Raed al Kadhimi. “I charge all the groups running to find someone who sacrifice their lives for Iraq like we have.”

The battle in Sadr City erupted when militants attacked what U.S. officials said were routine patrols. Al Kadhimi, however, described them as unjustified American raids into the sprawling neighborhood of two million, aimed at arresting al-Sadr’s militia members. Talks between al-Sadr’s representatives in the militia stronghold and interim Prime Minister Ayad Allawi’s government to bring about a peaceful resolution died amid the continuing attacks, al Kadhimi said.

U.S. troops are not finding it easy to disband al-Sadr’s Mahdi Army militia by force. The neighborhood was flush with militants and teens lighting fires and using hammers to break up asphalt on streets, then planting explosives in hopes of maiming U.S. tanks and armored vehicles rumbling past, witnesses said.

Other Sadr City residents blocked roads with rocks and tires while armed militants ran through alleyways in search of American targets to shoot with Kalashnikov assault rifles and rocket-propelled grenades.

U.S. warplanes fired flares overhead, as they sought to avoid anti-aircraft missiles. Arab television later broadcast footage of what appeared to be a U.S. tank towing another damaged tank away.

“There were only seven martyrs killed,” al Kadhimi claimed, referring to the Mahdi Army militants. “Most of those killed and wounded were ordinary people and children.”

Between the renewed fighting in Baghdad and action by Iraqi authorities to root out Mahdi Army members hiding in Najaf, the ceasefire brokered by Iraq’s top Shiite spiritual leader, Grand Ayatollah Ali al Husseini al Sistani on Aug. 27 is looking in danger of collapse.

Demonstrations

On Tuesday evening in Najaf, where al-Sadr is believed to be operating, more than 1,000 demonstrators marched for the third time this week near his office to demand that he and his militants leave.

They also chanted warnings that he not turn up for Friday prayers in neighboring Kufa at the mosque from which the radical cleric has built his movement.

In other attacks Tuesday, the U.S. military used airstrikes and shelling to quell insurgents in Fallujah who had fired on nearby American troop positions. Militants also attempted to kill Baghdad’s governor in a roadside bombing in the city. The attack killed two people but the governor escaped uninjured, the Interior Ministry said. Three of his bodyguards were injured.

To the north in Mosul, militants fatally shot the son of that city’s governor Tuesday.

But perhaps the most eerie attack came Tuesday afternoon in the raid on the Italian aid agency, Bridge to Baghdad. More than a dozen heavily armed kidnappers described by witnesses as “well dressed” in uniforms or suits forced two female Italian staff members and two Iraqi employees out of the aid organization’s office in a busy Baghdad commercial area and into waiting cars.

The abductions raised worries among foreigners who have felt relatively safe within the city limits despite more than 100 similar kidnappings nationwide since April aimed at driving out companies and troops allied with the U.S.-led coalition.