The Maryland State Police classified 53 nonviolent activists as terrorists and entered their names and personal information into state and federal databases that track terrorism suspects, the state police chief acknowledged yesterday.

Police Superintendent Terrence B. Sheridan revealed at a legislative hearing that the surveillance operation, which targeted opponents of the death penalty and the Iraq war, was far more extensive than was known when its existence was disclosed in July.

The department started sending letters of notification Saturday to the activists, inviting them to review their files before they are purged from the databases, Sheridan said.

"The names don't belong in there," he told the Senate Judicial Proceedings Committee. "It's as simple as that."

The surveillance took place over 14 months in 2005 and 2006, under the administration of former governor Robert L. Ehrlich Jr. (R). The former state police superintendent who authorized the operation, Thomas E. Hutchins, defended the program in testimony yesterday. Hutchins said the program was a bulwark against potential violence and called the activists "fringe people."

Sheridan said protest groups were also entered as terrorist organizations in the databases, but his staff has not identified which ones.

Stunned senators pressed Sheridan to apologize to the activists for the spying, assailed in an independent review last week as "overreaching" by law enforcement officials who were oblivious to their violation of the activists' rights of free expression and association. The letter, obtained by The Washington Post, does not apologize but admits that the state police have "no evidence whatsoever of any involvement in violent crime" by those classified as terrorists.

Hutchins told the committee it was not accurate to describe the program as spying. "I doubt anyone who has used that term has ever met a spy," he told the committee.

"What John Walker did is spying," Hutchins said, referring to John Walker Jr., a communications specialist for the U.S. Navy convicted of selling secrets to the Soviet Union. Hutchins said the intelligence agents, whose logs were obtained by the American Civil Liberties Union of Maryland as part of a lawsuit, were monitoring "open public meetings." His officers sought a "situational awareness" of the potential for disruption as death penalty opponents prepared to protest the executions of two men on death row, Hutchins said.

"I don't believe the First Amendment is any guarantee to those who wish to disrupt the government," he said. Hutchins said he did not notify Ehrlich about the surveillance. Ehrlich spokesman Henry Fawell said the governor had no comment.

Hutchins did not name the commander in the Division of Homeland Security and Intelligence who informed him in March 2005 that the surveillance had begun. More than a year later, after "they said, 'We're not getting much here,' " Hutchins said he cut off what he called a "low-level operation."

But Sen. James Brochin (D-Baltimore County) noted that undercover troopers used aliases to infiltrate organizational meetings, rallies and group e-mail lists. He called the spying a "deliberate infiltration to find out every piece of information necessary" on groups such as the Maryland Campaign to End the Death Penalty and the Baltimore Pledge of Resistance. When Hutchins called their members "fringe people," the audience of activists who filled the seats in the hearing room in Annapolis sighed.