Updated

A senior member of Saddam Hussein (search)'s ousted government is believed to be helping coordinate attacks on American forces with members of an Al Qaeda-linked terrorist group, a senior defense official said Wednesday.

Two captured members of Ansar al-Islam (search) have said Izzat Ibrahim al-Douri is helping to coordinate their attacks, the official said, speaking on condition of anonymity.

That information is the first solid evidence of links between remnants of Saddam's regime and the non-Iraqi fighters responsible for at least some of the attacks on U.S. forces and their Iraqi allies, the official said.

Pentagon officials say Ansar al-Islam, which operated in northern Iraq before its camp was destroyed during the war, poses one of the greatest threats in Iraq. Military commanders have said they believe hundreds of non-Iraqi fighters from Ansar have entered Iraq to fight the U.S.-led occupation, many of them through neighboring Iran.

Al-Douri is No. 6 on the most-wanted list of 55 Iraqis and was vice chairman of Saddam's Revolutionary Command Council. He was one of Saddam's few longtime confidants and his daughter was married to Saddam's son, Uday (search), who was killed in a raid by U.S. forces in July.

NBC News first reported the al-Douri link to Ansar al-Islam Tuesday night. Asked Wednesday about the report, Pentagon spokesman Larry Di Rita said he did not know anything about it.

Attacks on American troops have surged this week to about 33 per day, up from 26 per day last week and 15 per day in early September. A series of car bombings in and near Baghdad this week killed more than three dozen people.

U.S. officials have been searching for months for suspected links between Saddam loyalists and foreign fighters like Ansar members. President Bush and other U.S. officials have said they believe the bombings in Baghdad Monday were the work of Saddam loyalists, foreign fighters or both.

Pentagon officials say the Baghdad bombings -- four explosions in different parts of the city in less than an hour -- show a level of sophistication they had not seen before. Di Rita said the bombings indicated coordination "at least at the regional level."

The defense official who discussed the al-Douri link said he did not know if the al-Douri-Ansar alliance was responsible for the Baghdad bombings. He said military officials don't know to what extent al-Douri was coordinating attacks with Ansar.

Earlier this month, American forces captured a top associate of al-Douri in the town of Baqouba north of Baghdad.

U.S. officials have said for at least two months they suspect al-Douri of coordinating attacks on Americans but had not previously linked him to Ansar.

U.S. officials say Ansar al-Islam has links to Al Qaeda and has experimented with producing crude biological and chemical weapons. The group operated in a small section of northern Iraq surrounded by Kurdish-controlled areas which were outside Saddam's control.

Kurdish officials have long alleged that Saddam's government helped Ansar, but U.S. officials have said they haven't yet found definitive proof of that.