A Shiite insurgency appeared to be weakening Tuesday night as Iraqi forces moved to within 200 yards of the revered Imam Ali Shrine (search) and Iraq's defense minister once again demanded fighters loyal to a radical cleric surrender or face a violent raid.

U.S. warplanes, meanwhile, launched heavy bombing strikes on the volatile western city of Fallujah (search) on Wednesday, with explosions heard fo

U.S. forces have routinely bombed targets here it describes as insurgent safehouses or strongholds. A Marine spokesman, Lt. Col. Thomas V. Johnson, said he had no information about the attack in Fallujah, a Sunni stronghold some 40 miles west of Baghdad.

In Baghdad, assailants bombed the convoys of two government ministers in separate attacks that killed five people and a suicide bomber, but left the ministers unharmed, officials said.

The militant force, which once waged fierce battles with U.S. troops throughout the Old City and Najaf's vast cemetery, seemed considerably diminished in number and less aggressive after days of U.S. airstrikes and relentless artillery pounding.

Hundreds of insurgents have been spotted leaving Najaf in recent days, witnesses said. Those that remained appeared to have pulled back to the area around the shrine, where the fighting was concentrated on Tuesday, U.S. troops said.

Police say radical Shiite cleric Muqtada al-Sadr (search), who has not been seen in public for days, has fled the city.

His aides, however, vigorously denied that, saying al-Sadr was in a secret hideout here. Regardless, the fiery, charismatic cleric's absence from the battlefield may have withered his followers' morale.

U.S. warplanes bombed the Old City late Tuesday for the third night in a row, witnesses reported. Huge blasts rumbled throughout the city for about 10 minutes followed by gunbattles and smaller explosions.

Earlier Tuesday, fierce fighting broke out near the shrine compound, with rockets launched from U.S. helicopters kicking up clouds of smoke and debris. Bradley fighting vehicles patrolling the nearly deserted, bullet-scarred streets attacked militants, who responded with mortar fire and rocket-propelled grenades.

"We are under constant enemy small-arms, mortar, and RPG attack," said U.S. Lt. Chris Kent, whose unit was about 300 yards from the compound. "U.S. forces are consolidating positions to allow for future operations. Morale is very high."

Iraqi forces, accompanying U.S. troops into the Old City for the first time in recent days, combed through the neighborhood, approaching as close as 200 yards to the shrine, controlled by militants loyal to al-Sadr.

Both the Iraqi government and the U.S. military say no military moves are being made without the approval of interim Prime Minister Ayad Allawi.

Defense Minister Hazem Shaalan, addressing Iraqi National Guard troops in Najaf, said Tuesday that Iraqi forces would head toward the shrine "tonight" to await the signal for a raid or the capitulation of the militants.

"When your brothers approach the holy shrine compound, they will direct calls of mercy to those (militants) to surrender," Shaalan told the troops. "They have hours to surrender."

By late Tuesday, there was no indication Iraqi forces had advanced on the shrine.

Shaalan made a similar threat a week ago, saying the government could raid the shrine by the end of the day last Wednesday to free it of "its vile occupation." The government later backed down and said it would work for a peaceful solution.

Any raid on the shrine, the holiest Shiite site in the country, risked igniting a massive Shiite rebellion throughout Iraq against the fledgling interim government, already battling a persistent and bloody Sunni insurgency.

"I tell Shaalan to throw his new declaration in the same garbage that he already threw his earlier declarations in," al-Sadr aide Sheik Aws al-Khafaji told Al-Jazeera television. But other al-Sadr lieutenants reiterated their appeal for talks, a request the government has repeatedly rejected.

"We are ready to negotiate to end this crisis and the suffering of our persecuted people ... but this government doesn't want negotiations," said Sheik Ali Smeisim, a senior al-Sadr aide.

The militants have repeatedly accused U.S. forces of damaging the shrine during the fighting. The U.S. military accused the militants of launching attacks from holy sites, but said it has restrained itself from attacking those positions.

The military released aerial photos Tuesday purportedly showing a complete militant mortar system set up just outside the shrine compound.

Iraqi officials have said that any raid on the shrine would be conducted by Iraqi forces, since the presence of U.S. troops at the holy site would future inflame Shiites here.

In other violence, clashes between British forces and al-Sadr militants in the southern city of Amarah killed eight people and injured 18 others, said Dr. Saad Hemood, of the Zahrawi General Hospital.

The fighting started when militants attacked a British foot patrol with small arms and fired mortar rounds at a building housing British troops, residents said.

Residents said British warplanes bombed the city, but Squadron leader Spike Wilson, a British military spokesman, said no planes were used in Amarah and he had no reports of coalition casualties.

In southern Baghdad, a car bomb exploded in the Qadisiyah neighborhood as Environment Minister Miskhat Moumin was passing through in a convoy, ministry spokeswoman Dalal Ali said. Moumin escaped unharmed, Ali said.

Four bodyguards and a suicide bomber were killed in that blast and two other people were injured, Interior Ministry spokesman Col. Adnan Abdul-Rahman said.

In a second attack about the same time in the western Baghdad district of al-Khadra, a roadside bomb exploded beside Education Minister Sami Mudhafar's convoy, killing one of his bodyguards and wounding two others, police said.

The convoy was heading to work at the time and the minister was not injured, a bodyguard who survived the attack said on condition of anonymity.

In a statement posted on an Islamic Web site, Jordanian militant Abu Musab al-Zarqawi's Tawhid and Jihad group purportedly claimed responsibility for the attack on Moumin. The claim's authenticity could not be verified.

Insurgents have repeatedly targeted top officials for assassination, accusing them of collaborating with U.S. forces here.

Also in Baghdad, assailants fired a rocket-propelled grenade at a U.S. patrol on Monday night, killing one soldier and wounding two others, the military said Tuesday. A second soldier was killed early Tuesday near Fallujah when the vehicle he was in rolled over, the military said. As of Tuesday, 962 U.S. service members have died since the beginning of military operations in Iraq in March 2003, according to the U.S. Defense Department.

Also Tuesday, a militant group calling itself "The Islamic Army in Iraq" said it had kidnapped Italian journalist Enzo Baldoni and could not guarantee his safety unless Italy announced within 48 hours it would withdraw its 3,000 troops, according to a video and statement sent to Al-Jazeera.

Italy said its troops would remain, but it would work for Baldoni's release.

"We are committed to obtaining the freedom of Mr. Baldoni, who is in Iraq for private work as a journalist and therefore absolutely not connected to our government," Italian Premier Silvio Berlusconi's office said in a statement.