American soldiers on the road to Baghdad fought bloody street-to-street battles with militants loyal to Saddam Hussein while tense troops in southern Iraq shot and killed seven women and children when the driver of a van failed to stop at a checkpoint.

The civilian deaths, following days of ambush attacks, may damage coalition efforts to win over the Iraqi people.

U.S.-led forces launched missiles Tuesday toward Baghdad and the holy Shiite Muslim city of Karbala to the southwest, and circling warplanes bombed targets in the area. Buildings in the capital shuddered in some of the strongest blasts since the air war began March 20. Smoke billowed from the capital's Old Palace presidential compound.

Among the targets, U.S. officials said, was a complex that serves as the office of the Iraqi National Olympic Committee, where Iraqi dissidents say Saddam's son Odai runs a torture center.

The coalition has relentlessly targeted Republican Guard positions in and around Baghdad in preparation for the war's likely decisive battle. U.S. forces battled some of these fighters Monday in the Euphrates River town of Hindiyah, about 50 miles south of the capital. Troops seized tons of ammunition and hundreds of weapons at the local Baath party headquarters, along with maps showing Iraqi military positions and the expected route of the U.S. attack.

To the south, Marines traded fire Tuesday with hundreds of Iraqi fighters in the town of Diwaniyah. Other units fought to isolate the holy Shiite city of Najaf in an ongoing effort to protect U.S. supply lines. A series of ruse attacks by militants in civilian clothes have made the trek north increasingly dangerous for coalition troops.

Monday's fatal shooting happened at a U.S. Army checkpoint near Najaf, about 20 miles north of Saturday's suicide attack. Coalition officials said soldiers motioned for an approaching van to stop, but the driver ignored them. Troops first fired warning shots, then shot into the engine and then the passenger compartment as a last resort, according to a statement from U.S. Central Command, which oversees the war in Iraq.

The van was carrying 13 women and children, and seven were killed, the statement said. But The Washington Post, whose reporter is embedded with the Army's 3rd Infantry Division, said 15 people were in the vehicle and 10 were killed, including five small children.

The newspaper described the vehicle as a four-wheel-drive Toyota crammed with the Iraqis' personal belongings. In its account of the shooting, the Post quoted an Army captain as saying the checkpoint crew did not fire the warning shots quickly enough.

Central Command said initial reports indicated the soldiers had acted properly. Spokesman Brig. Gen. Vincent Brooks attributed the discrepancy in the number of dead to ''the fog of war.''

He said the coalition has tried to avoid harming civilians and blamed the deaths on the Iraqi regime's guerrilla tactics and its practice of using women and children as shields.

''The blood is on the hands of the regime. If there's a question of morality, it really should go back to the regime,'' Brooks said.

Another Iraqi was killed Tuesday in a similar checkpoint shooting near the south-central town of Shatra, Central Command spokesman Navy Capt. Frank Thorp said.

Such incidents are likely to stoke opposition to the U.S.-led invasion among Iraqis in the Shiite region, where Washington had hoped for a popular uprising against Saddam's Sunni Muslim government.

U.S.-led troops moving north toward Baghdad have focused much of their energy on rooting out fighters with the ruling Baath Party militia and the Fedayeen - Saddam's most trusted paramilitary militia. They have also distributed rations to civilians, and they say winning the hearts and minds of the Iraqi people is a priority.

In the town of Diwaniyah, about 80 miles southeast of Baghdad, Marines fought with hundreds of Iraqi fighters who fired on them from inside buildings. At least 20 Iraqis were taken prisoner; some simply surrendered.

Iraqi Information Minister Mohammed Saeed al-Sahhaf claimed Tuesday that coalition warplanes bombed two buses carrying ''human shields,'' including Americans and Europeans, near the Jordanian border. Central Command said it was unaware of the incident. Peace groups in Jordan said they had heard nothing about such an attack.

Iraq also publicly denied a report that Saddam's family had fled the country. A statement on Iraqi TV called the report ''a rumor circulated by the U.S. Defense Department.''

Iraqi TV aired footage Monday of Saddam and his sons Odai and Qusai, but there was no way of determining when it was shot. U.S. intelligence has not confirmed Saddam survived an attack early in the war.

President Bush warned that Saddam ''may try to bring terror to our shores.'' The United States is acting to prevent such threats, he said, while offering assurances that the war remains on track. ''Day by day we are moving closer to victory,'' he said.

In northern Iraq, commanders said forces searching the recently captured compound of Muslim extremist group Ansar al-Islam found documents, computer discs and other material belonging to Arab fighters. The Bush administration has longed claimed Ansar is linked to the al-Qaida terrorist network, but there has been no indication it has ties to Saddam's regime.

Near the southern port of Basra, warplanes from the aircraft carrier USS Kitty Hawk dropped bombs on an Iraqi presidential yacht and another ship, Navy officials said Tuesday. Brooks, the Central Command spokesman, said British forces in Basra had destroyed a number of Iraqi tanks and personnel carriers, rescued two Kenyan truck drivers who had been held by Iraqis since last week and captured an Iraqi general who had provide information about battlefield tactics. He gave no other details about the general.

An Iraqi prisoner was shot to death after he reached for a Marine's weapon while being questioned, Central Command spokesman Lt. Cmdr. Charles Owen said Tuesday. He had no other details.

Also Tuesday, the coalition lost an S-3B Viking plane when it veered off the flight deck of the aircraft carrier USS Constellation and slipped into the Persian Gulf. Both pilots aboard were rescued, and suffered only minor injuries.