Hundreds of allied warplanes pounded Iraq Monday, destroying a major bridge, taking out Scud missile launchers and choking off traffic to the military headquarters in Basra, U.S. officials said.

The officials also said Iraqi jets that have fled to Iran pose little threat because their pilots are inexperienced and cannot be kept combat-ready.In another indication of the war's toll on Iraq, Baghdad said Monday it will begin drafting all 17-year-old males. Last month, Iraq lowered the conscription age from 18 to 17, but exempted youths still in school.

Thousands of Iraqi civilians have been killed or wounded by allied air raids, Iraqi Religious Affairs Minister Abdullah Fadel said Monday in Baghdad.

It was the first time a senior government official spoke of such high war casualties. Fadel said he could not give precise figures. Previous Iraqi reports put civilian casualties at about 650 dead and 750 wounded.

Allied pilots, meanwhile, flew nearly 3,000 sorties in what the U.S. Command described as an intensification of the air campaign leading up to a ground assault expected in the next few weeks.

The Pentagon, meanwhile, confirmed that two American POWs, including the sole female captive, have been moved to Basra, apparently as "human shields" against allied attacks.

An Iraqi prisoner of war described taking two Americans to Basra. The descriptions appeared to match those of Army Spec. Melissa Rathbun-Nealy, 20, of Grand Rapids, Mich., and Spec. David Lockett, 23, of Fort Bliss, Texas, who disappeared in Saudi Arabia on Feb. 1.

In Riyadh, the Saudi capital, U.S. officials said 40 percent of Iraq's air force is believed out of commission, including the planes that fled to Iran.

No Iraqi planes are known to have escaped into Iran in the past few days, the officials said. They said 147 Iraqi planes were in Iran - including 121 combat planes, many of them among Saddam Hussein's best.

Baghdad was believed to have about 700 aircraft at the outset of the Persian Gulf war. The allies say they've downed 34 planes and confirmed the destruction of 99 on the ground.

Salah Nasrawi, the AP correspondent in Baghdad, said the Martyrs Bridge, damaged in a weekend raid, was destroyed Monday. Three of the six bridges over the Tigris River in central Baghdad have now been destroyed.

Marine Brig. Gen. Richard Neal told reporters in Riyadh Monday that allied pilots had flown 2,900 sorties in the last 24 hours. More than 69,000 sorties have been flown by allied bombers in the 26-day-old war, he said.

Neal said allied raids had succeeded in halting most of the military traffic between Baghdad and the port city of Basra, the Iraqi military headquarters.

"We have struck some of the key bridges going into Basra. Perhaps there still is (military) traffic . . . but in fact it can't get into Basra," Neal said. "We do feel we have significantly cut down the flow of military goods and equipment."

Asked about reports of large numbers of civilian casualties in Basra, Neal blamed Saddam for placing anti-aircraft artillery and other military hardware in residential neighborhoods and civilian buildings.

"By moving into civilian type structures, they assume responsibility for civilian casualties," Neal said, adding that Basra was "a military town in the true sense."

Neal said he believed some of the bombed out buildings being shown to Western journalists in Basra were actually damaged during the Iran-Iraq war and not by allied air strikes.