City Councilman William Peduto said he will not retract his accusation that the Pittsburgh Organizing Group is responsible for the vandalism of several businesses last week in Shadyside.

He also said yesterday he would not respond to what he perceives as threats by the organization, sometimes referred to as POG.

The threats, the councilman said, came in the form of about a half-dozen phone calls last week from POG members. The callers demanded that Mr. Peduto hold a news conference to retract the accusations.

The tone of the calls is what Mr. Peduto perceived as threatening.

"I won't retract or respond to threats," Mr. Peduto said. "It goes against the principles I'm trying to run this office from."

Patrick Young, a member of the self-described anarchist movement of POG, said the organization denies any involvement in the vandalism.

Windows of at least two businesses along Walnut Street were smashed with large rocks. Others were sprayed with graffiti signifying opposition to the convening last week of the Group of Eight, or G-8 summit of world leaders in Heiligendamm, Germany.

Mr. Young, 23, admitted that POG stages protests of the G-8 summit. He also said it opposes the war in Iraq.

But, he said, "POG had nothing to do with Shadyside. We don't participate in property destruction. We don't organize it.

"We have no knowledge of the identities of or the motivation of the alleged [suspects]."

In a message to the councilman posted on the group's Internet site, and copied to the Pittsburgh Post-Gazette, the group denied involvement in vandalism and demanded Mr. Peduto's retraction.

Mr. Peduto said he read a police report that said the perpetrators of last week's vandalism were believed to be associated with the anti-war group in Oakland. He referred to vandalism May 5 at a military recruiting station that was broken into and ransacked, and similar acts later that day at Carnegie Mellon University's Wean Hall.

In each case, the councilman said, witnesses said they saw 10 to 15 men and women wearing black hoods and masks.

Similar incidents were reported by witnesses and captured on video surveillance cameras Jan. 13 at a Marine Corps recruiting station, April 3 at a similar station in Shadyside, and April 14 at the same station.

The vandals spray-painted anti-war commentary signed with the letter A, an anarchist signature, Mr. Peduto said.

The councilman deduced from those reports that the culprits fit the same description as those from incidents in which POG has claimed credit.

"They're losing the one elected official they had because of the accusations and tactics in the field. They're proving their actions don't work and actually are counterproductive," Mr. Peduto said.

"They're saying it's irresponsible for me to isolate any one group. What other group of anarchists are there in this city?"

Mr. Young said he estimates there are as many as 500 anarchists in the Pittsburgh area. Some of them posted acknowledgement of the Shadyside incident on a Web site.

"Because we're one of largest radical organizations in Pittsburgh, we get blamed for a lot of things we didn't do," he said.

He pointed to a slogan frequently posted for its irony and satire that says, "Hey POG, why the heck did you do that?" The phrase serves as an Internet link to comments and statements by POG members.

"There are hundreds of thousands of people who protest against the G-8. To have the finger pointed at us undermines the scope of the anti-war global justice movement," Mr. Young said.

Pittsburgh police have not commented on investigations of the most recent incidents.