Intelligence officials have verified reports that foreign fighters have been entering Iraq to engage U.S. forces, a government source told Fox News Friday.

The report comes one day after the U.S. Military launched air strikes on what it said was a "terrorist training" camp in Al Asad (search). Central Command (search) said about 70 fighters, including many foreigners, were killed in the attack.

Senior defense officials now say that some of the combatants came from Saudi Arabia, Yemen, Jordan, Syria and other Arab nations.

Although military officials believe most foreign fighters entered Iraq just before or just after the recent war in Iraq, intelligence officials now acknowledge that there is still a "trickle" of foreigners entering the country to fight against the Americans

There is no hard evidence to link any of these fighters to Al Qaeda (search) terrorists, but the source said that many of them are thought to be Islamic extremists and Al Qaeda sympathizers.

The presence of Yemenis and Saudis in Iraq may indicate links to Al Qaeda, which draws heavily from a population of disaffected Muslim extremists in both countries.

Usama bin Laden was a Saudi citizen before his citizenship was revoked, and Yemen is his ancestral homeland.

The source said the presence of Saudi fighters is particularly suspicious, because the Saudi government and former Iraqi dictator Saddam Hussein eyed each other with great suspicion. U.S. troops were positioned in Iraq in the early 1990s, in part to discourage any Iraqi designs on invading Saudi Arabia.

Central Command announced Friday morning that it had captured 74 Al Qaeda sympathizers in a raid near Kirkuk, but Lt. Gen. David McKiernan, commander of the coalition joint task force, later backed off that assertion in a briefing, saying there was no way of knowing with whom the fighters -- presumably foreigners -- were associated.

In the meantime, U.S. forces continue to "exploit" the terror camp at Al Asad, where they are gathering intelligence that may lead to them other groups of combatants and possibly other staging areas used to prepare attacks on American forces.

Fox News' Bret Baier and Ian McCaleb contributed to this report.