The U.S. Air Force unleashed some of the biggest bombs in its inventory against suspected insurgent targets in central Iraq, escalating the coalition's anti-guerrilla campaign, the U.S. military said Wednesday.

Firing could be heard after sundown Wednesday in the Iraqi capital, as the military pursued its "Operation Iron Hammer" campaign. An American general said the offensive was to intimidate the guerrillas by "planting the seeds of doubt in their minds" that they can ever overcome U.S. power.

Two 2,000-pound, satellite-guided bombs were dropped late Tuesday near Baqouba, 30 miles northeast of Baghdad, on "camps suspected to have been used for bomb-making," said Maj. Gordon Tate, a spokesman for the 4th Infantry Division.

Near the northern city of Kirkuk, fighter-bombers dropped 1,000-pound bombs on "terrorist targets," he said without elaborating.

Elsewhere, insurgents fired on a U.S. supply convoy north of Samara on Wednesday, witnesses said. American troops returning fire killed two Iraqis, including a teenager, the witnesses said.

There was no confirmation from the U.S. military, but the sounds of gunfire could be heard during a telephone conversation with witnesses.

A roadside bomb exploded Wednesday in the southern city of Basra, damaging a British civilian vehicle but causing no casualties, according to British spokesman Maj. Hisham Halawi.

In Baghdad, Brig. Gen. Martin Dempsey, commander of the 1st Armored Division, told The Associated Press the offensive was designed to demonstrate the effectiveness of U.S. firepower.

"We felt that the enemy had begun to act with a little more impunity than we want him to have," said Dempsey, whose troops are responsible for security in the capital. "We've just raised the stakes a bit by planting the seeds of doubt in their minds."

In recent days, U.S. forces have used heavy artillery, battle tanks, attack helicopters, F-16 fighter-bombers and AC-130 gunships to pound targets in central and northern Iraq.

Iraqi civilians living near the affected areas have expressed outrage over the use of such overwhelming force.

"[The Americans] called on us from the tanks to stay at home," Hamziya Ali, a housewife living near the plant, said Wednesday. "But me and my children spent the night shaking. We do not want to be their targets."

Some senior U.S. officers have privately expressed fears that people in Iraq and the Arab world will see the escalation of attacks against insurgents as no different from Israeli crackdowns on the Palestinians.

Dempsey, like other senior commanders in Iraq, said he believes the attacks against American forces have been carried out primarily by supporters of Saddam Hussein without any significant participation by foreign fighters.

He also expressed doubt the conflict would escalate into a general uprising. Some Iraqis have speculated that unemployment, estimated between 60 percent and 70 percent, is driving more people into the insurgency.

"I don't think I've seen any sign of a nascent insurgency by disenchanted youths," Dempsey said. "Is that a possibility? Yes, it is if we get this wrong. ... That's why we're doing everything we can to ensure that doesn't happen."

The aggressive tactics followed an upsurge in guerrilla activity and a sharp rise in the number of coalition casualties. About 70 allied soldiers have died in November, already making it the deadliest month since April, when 73 troops died. President Bush declared major combat over May 1.

Rebels have also threatened Iraqis who cooperate with the U.S. occupation. On Tuesday, gunmen assassinated the Education Ministry's director for Diwaniyah province, Hmud Kadhim, government officials said Wednesday. No group claimed responsibility.

U.S. authorities offered a $10 million reward Wednesday for information leading to the capture of one of Saddam's top aides who is believed to be behind some of the attacks on coalition forces.

Izzat Ibrahim al-Douri, No. 6 on the list of 55 most-wanted Iraqis, was the vice chairman of the Revolutionary Command Council and was in charge of Iraq's northern defenses shortly before the U.S.-led war began March 20.