BAGHDAD, Iraq (CNN) — U.S.-led forces were on the lookout Tuesday for two wanted men in volatile bases of the Iraqi insurgency — Shiite Muslim cleric Muqtada al-Sadr in Najaf and militant Abu Musab al-Zarqawi in Fallujah, Brig. Gen. Mark Kimmitt said.
Also Tuesday, several nations were trying to use diplomacy to free hostages who have been kidnapped by insurgents in Iraq.
Forty people from 12 countries are being held by Iraqi militants, said Dan Senor, spokesman for the U.S.-led Coalition Provisional Authority.
In the past 24 hours, at least two Marines were killed in Fallujah, west of Baghdad. A U.S. chopper made an emergency landing Tuesday due to groundfire outside the central Iraqi city, the Pentagon said. Three soldiers were wounded, the U.S. military said.
A quick reaction force secured the crew, and the aircraft was destroyed before insurgents could gain access to it, Kimmitt said.
U.S. troops are trying to quell the uprisings, moving throughout the country where needed, he said.
“We still have some tough fighting ahead of us,” Kimmitt said. “It is not completely calm throughout this country.”
He said “significant” and “powerful” U.S. forces had massed outside the Shiite holy city of Najaf, where al-Sadr is based.
The cleric, who has led an uprising the U.S.-led coalition is trying to crush, might be anticipating a fight. He was seen Tuesday leaving a Najaf mosque.
Al-Sadr told an Arabic-language TV station in Lebanon he is “ready to sacrifice [myself], and I call on the [Iraqi] people not to allow my death to cause the collapse of the fight for freedom and an end to the occupation.”
Kimmitt said U.S. troops are conducting “preparatory operations” and when necessary will “go after him [al-Sadr] and his militia to end this violence.”
Kimmitt later said cities such as Najaf and Karbala with their important Shiite shrines are not targets. He said Sadr and his militia, the Mehdi Army, are “trying to intimidate through a barrel of a gun the vast majority of the people of Iraq.”
“They will be hunted down. They will be captured,” Kimmitt said.
U.S. forces released a top al-Sadr aide, Sheikh Hazem al-Araji, after questioning because the coalition said it concluded he was not involved with the violence and was inclined to promote dialogue.
U.S. forces also have faced bitter fighting with Iraqi militants in the Sunni stronghold of Fallujah after the March 31 killings and mutilations of four American contractors. Kimmitt called the situation stable but said there have been “provocative” actions by insurgents.
Marines on Tuesday seized “two known terrorists” and three others suspected of terror activity in a raid near Fallujah, according to a statement from the 1st Marine Division.
On Monday night, at least two U.S. Marines were killed and at least eight others wounded in an intense exchange with Iraqi insurgents in Fallujah, according to pool reporters embedded with the 1st Marine Expeditionary Force.
Coalition blames ‘foreign fighters’ in Fallujah
Senor said that al-Zarqawi, a Jordanian-born militant with suspected al Qaeda ties who is believed to be spearheading terror attacks in Iraq, is nearby or in Fallujah, long an epicenter of anti-coalition sentiment.
“We believe Fallujah right now is a hotbed for foreign fighters in Iraq,” he said, adding that residents would like to rid themselves of the burden.
“The problem here is with the foreign fighters, the international terrorists, people like al-Zarqawi, who we believe to be in Fallujah or nearby, and those Iraqis who would support the operations of the foreign fighters or the terrorists.”
The coalition has said that it found a letter al-Zarqawi wrote to al Qaeda leadership in Afghanistan in which he bragged of terror attacks outside northern Iraq and called for fomenting civil strife by attacking Shiites.