Fallujah, Iraq ? U.S. troops, on the verge of gaining control of the city, fought pockets of resistance in this former militant stronghold Wednesday and uncovered what the Iraqi commander said were “hostage slaughterhouses” in which foreign captives had been killed.

Insurgents sought to open a second front, mounting attacks outside Fallujah. They also kidnapped three relatives of Prime Minister Ayad Allawi and reportedly threatened further revenge against the leader. Militants also claimed to have abducted 20 Iraqi National Guard troops in Fallujah.

Throughout the day, Americans hit the militants with artillery and mortars, and warplanes fired on the city’s main street and market as well as Jolan, one of several neighborhoods where troops were skirmishing with militants.

In what could be a sign of progress, the Marines began turning over Jolan to Iraqi forces, signaling that Marines consider the area relatively secure. Jolan was considered one of the strongest positions held by militants inside Fallujah.

The top U.S. commander in Iraq, Gen. George Casey, told President Bush on Wednesday that his troops were “making very good progress” securing Iraq.

“He said that things are going well in Fallujah,” Bush said, adding that his Iraq commanders had not asked for more troops. The U.S. military has sent up to 15,000 U.S. and Iraqi troops into the battle, backed by tanks, artillery and attack aircraft.

Lt. Gen. John F. Sattler, the commanding general of the 1st Marine Expeditionary Force, said insurgents had been reduced to “small pockets, blind, moving throughout the city. And we will continue to hunt them down and destroy them.”

In Fallujah, at least 71 militants had been killed by early Wednesday, the third day of intense urban combat, the military said. As of Tuesday night, 10 U.S. troops and two members of the Iraqi security forces had been killed. Marine reports Wednesday said 25 American troops and 16 Iraqi soldiers were wounded. There was no new report Wednesday on U.S. military deaths.

One Marine officer estimated U.S. and Iraqi forces controlled about 70 percent of the city, but the commander of the Iraqi force said he believed the figure was closer to 50 percent.

The Iraqi commander, Maj. Gen. Abdul Qader Mohammed Jassem Mohan, announced the seizure of the abandoned houses in northern Fallujah that he said contained hostages’ documents, CDs showing captives being killed, and black clothing worn by militants in videos.

It appeared troops did not find any of the at least nine foreigners still in kidnappers’ hands — including two Americans. “We have found hostage slaughterhouses in Fallujah that were used by these people,” Mohan said.

Gunmen kidnapped three of Allawi’s relatives from their Baghdad home — his cousin, Ghazi Allawi, the cousin’s wife and their daughter-in-law, Allawi’s spokesman said. A militant group calling itself Ansar al-Jihad threatened to behead them in 48 hours unless the Fallujah siege is lifted.

Early today, a videotape posted on an Islamist Web site purportedly by Fallujah militants vowed to take revenge on Allawi and Defense Minister Hazem Shaalan al-Khuzaei, saying both had displayed “meanness toward those who are defending their home.”