Authorities announced Thursday they had arrested two leaders of an Albany mosque and charged them in a sting operation with helping a government informant who purportedly wanted to sell a shoulder-fired grenade launcher to terrorists.

Yassin Muhiddin Aref, 34, the imam, or spiritual leader, of the Masjid as-Salam mosque, and Mohammed Mosharref Hossain, 49, who worships at the mosque, were charged in U.S. District Court here with concealing material support for terrorism and participating in a money-laundering conspiracy.

Deputy Attorney General James B. Comey said at a Washington news conference that the arrests sent "a disrupting message" to potential terrorists. "Anyone engaging in terrorist planning would be very wise to consider whether their accomplice is not really one of our guys," he said.

He also stressed that the case does not involve an actual terrorist plot and is not related to the current alert about al Qaeda attacks. "The terrorist plot in this case is one that the government's agent, the cooperating witness, represented to be underway. It was not real," he said.

Federal officials said the arrests follow a year-long FBI investigation in which Aref and Hossain agreed to launder money for the informant, who told them that the weapon he was selling would be used against a Pakistani diplomat in New York City as punishment for that country's cooperation with U.S. anti-terrorist activities.

Members of both men's families denied the charges. "What they are saying is absolutely, 100 percent false," said Hossain's wife, Mossamat.

Police kept watch in front of the small brick mosque on Central Avenue, a diverse thoroughfare that leads to the New York state capitol.

Later in the day, just before evening prayer, Faisal Ahmad, whose father is the president of the mosque, said at a news conference that he hoped the community would not rush to judgment. "Let us follow the due process of law and let not the actions of a few individuals be used to brush an entire community as terrorists," he said.

Charles Wilder, 41, sitting on a stoop across the street from the mosque, said the arrests showed that "terrorism can happen anywhere, even a little town like Smallbany."

But many who worship at the mosque said they do not believe the charges.

"This is about politics. This is about scaring people," said a Sudanese immigrant who runs a nearby grocery store. Asked why he would not give his name, he said, "I don't want them coming to me next."

Those who know the two men expressed shock at the allegations.

Hossain "comes across as this great American; his life was the American dream," said Cleo Junco, 55. She owns a building a few blocks from the mosque where she said Hossain lives with his wife and five children. Hossain owns a local pizza parlor and, according to an Albany Times Union profile, immigrated from Bangladesh in 1985.

Junco said that after the Sept. 11, 2001, terrorist attacks, Hossain gave her son a copy of the Koran. "He wanted us to see that Islam is not a belligerent religion," she said.

Court documents say that at a videotaped meeting Nov. 20, the informant showed Hossain a picture of an RPG-7, an antitank weapon, and talked about using it. The unidentified informant, a convicted felon working for the government, told Hossain and Aref he was affiliated with Jaish-e-Mohammed, an Islamic extremist group in Pakistan that the United States has designated a terrorist organization, according to court records. The men were allegedly paid $65,000 in cash for their participation.

Law enforcement sources also said Hossain and Aref have ties to Ansar al-Islam, the Iraq-based terrorist group with links to al Qaeda, but court documents make no mention of such connections.

Eggen reported from Washington. Researcher Julie Tate also contributed to this report.

Yassin Muhiddin Aref, top, and Mohammed Mosharref Hossain leave a federal courthouse.