Federal authorities today unsealed a criminal complaint against a British national who was arrested in London yesterday, alleging that he used Internet service providers in the United States to raise money for terrorists and possessed classified plans for a U.S. Navy battle group operating in the Persian Gulf.

The complaint indicates that a U.S. sailor aboard one of the ships in the battle group was effectively acting as a spy for Muslim militants, but it does not explicitly say that the person provided the classified plans.

In a press conference in New Haven, Conn., U.S. Attorney Kevin J. O'Connor said the United States was seeking the extradition from Britain of Babar Ahmad, a 30-year-old British citizen of Pakistani origin, on charges including conspiracy to provide material support to terrorists, money laundering and solicitation to commit a crime of violence. Ahmad was also charged with conspiracy to support the Taliban, the radical Muslim group that ruled Afghanistan and harbored the al Qaeda terrorist network before being ousted in a U.S.-backed offensive in November 2001.

Ahmad, who reportedly works with computers at a London college, told a court there today that he did not understand the charges against him, saying, "It's all a bit confusing to me." He said he did not want to be sent to the United States, and he was remanded in custody for a week while the extradition request is considered.

O'Connor said the case was intended in part to send a message to terrorists that the United States will be "more patient and more persistent" than they are and will root them out wherever they might be, including on the Internet.

"No matter where they're hiding -- be it in a cave, be it in the ground, be it in a safe house or the dark corners of cyberspace -- law enforcement is there as well," O'Connor told the news conference. He said the United States would "continue to engage in the war on terrorism no matter where it takes us -- cyberspace, holes in the ground or anywhere else."

The complaint in the case, a 31-page affidavit from the Bureau of Immigration and Customs Enforcement that was unsealed this morning, alleges that Ahmad operated a series of pro-jihad Web sites between 1997 and 2003 through Internet service providers in Connecticut and Nevada.

O'Connor said the Web sites were used to "solicit financial support for terrorist organizations including the Taliban and the Chechen mujaheddin," Islamic fighters battling for the independence of the Russian republic of Chechnya.

Among the evidence collected during a nearly three-year investigation of Ahmad were e-mails linking him with a Chechen guerrilla leader who helped plan a deadly attack on a Moscow theater in 2002, O'Connor said.

Between November 2001 and March 23, 2002, the complaint says, one of Ahmad's Web sites instructed Pakistanis living in the United States, Canada and Britain on how to secretly enter Afghanistan to fight for the Taliban, which has been waging an insurgency against U.S. and Afghan government forces since the group was ousted from power.

In December 2003, the complaint says, British authorities seized a floppy disk from Ahmad that contained detailed information on a U.S. naval battle group that was heading to the Persian Gulf in April 2001 on a mission to enforce sanctions against Iraq and conduct operations against Afghanistan and al Qaeda.

The plans, dated April 12, 2001, and classified at the time, described the battle group's anticipated passage through the Strait of Hormuz at night on April 29, 2001, according to the complaint. The disk also contained a drawing of the group's formation for that passage, the name and location of each ship and information on their vulnerability to terrorist attack, with specific examples of how such attacks might be carried out. For example, the document said, "they have nothing to stop a small craft with RPG [rocket-propelled grenade] etc., except their Seals' stinger missiles."

No attack on the battle group was actually carried out, O'Connor said.

From late 2000 through 2001, Ahmad exchanged e-mail with a person who described himself as an enlistee in the U.S. Navy on active duty in the Middle East. The investigation showed that the enlistee was communicating from the USS Benfold, a guided missile destroyer based in San Diego as part of the Pacific Fleet and assigned to the battle group that was the subject of the planning document. The complaint does not specify that the enlistee was the source of the April 12, 2001, information on the battle group.

However, it says Ahmad received an e-mail from the Benfold in July 2001 in which the enlistee expressed anti-American sentiments, praised Islamic militants fighting in "the lands of jihad" such as Afghanistan, Bosnia and Chechnya, and lauded the October 2000 terrorist attack on the USS Cole in a Yemeni port. The attack on the Cole was carried out by al Qaeda and killed 17 U.S. sailors.

The July 2001 e-mail discussed a briefing aboard the ship on preventing terrorist attacks similar to the suicide bombing of the Cole, the complaint says.

O'Connor described the enlistee as "sympathetic to the jihad movement," but said he could not provide any further details.

"We've identified the individual, and no charges have been announced against that individual at this time," O'Connor said.

A Navy spokesman at the Pentagon, Lt. Cmdr. Cappy Surette, said the sailor "has no current affiliation with the Navy," having left the service about two years ago. He said the Naval Criminal Investigative Service is providing assistance to the investigation.

The battle group to which the sailor belonged consisted of about 12 ships led by the aircraft carrier USS Constellation, Surette said.

A spokesman for the Bureau of Immigration and Customs Enforcement, Dean Boyd, said the sailor's correspondence with Ahmad is the subject of "an ongoing investigation." Investigators are also looking into persons in the United States who may have contributed funds to Ahmad or helped advance his causes, Boyd said.

He said investigators are reviewing thousands of e-mails to Ahmad's Web sites from around the globe and sifting through about 500 gigabytes of electronic data.

In addition to Immigration and Customs Enforcement and the Navy, agents from the IRS, FBI and the Defense Criminal Investigative Service are participating in the investigation of the Ahmad case.

If convicted, Ahmad faces up to life imprisonment on the charge of conspiracy to provide material support to terrorists, as well as penalties of 10 to 20 years in prison on the other charges.