JERUSALEM—Israel’s domestic security agency has been operating a secret unit designed to monitor and infiltrate opposition to the government’s withdrawal policy from the West Bank and Gaza Strip.

The secret unit was established in February 2005 as the government prepared for the withdrawal from the Gaza Strip and northern West Bank and the expulsion of 10,000 Jews. Officials said the Israel Security Agency unit, authorized to infiltrate protest groups, was also designed to monitor the Internet.

"There will be attorneys in every relevant district, and they can accompany the investigations and provide immediate advice to the police because of the sensitivity involved in the realm of expression," Shai Nitzan, deputy state prosecutor for special operations, said.

Nearly two years later, the government and some panel members have refused to acknowledge the ISA unit. But Knesset member Michael Eitan, former chairman of the Constitution and Law Committee, said the unit continues to operate, although without parliamentary oversight.

"This was an intelligence unit," Mr. Eitan told Israeljustice.com in mid-January 2007. "What’s it our business to oversee this?"

The secret intelligence unit was discussed in a closed emergency session of the Knesset Constitution and Law Committee on March 1, 2005. A transcript of the hearing was recently obtained by Israeljustice.com.

"The government conducted a meeting and has made a decision to establish a special unit in the Justice Ministry," Mr. Eitan told the committee during the emergency session.

Officials said Mr. Nitzan has headed the secret ISA unit under the jurisdiction of the Justice Ministry. They said Mr. Nitzan reports to Attorney General Menachem Mazuz and the unidentified legal adviser of the ISA.

Neither the ISA nor the Justice Ministry agreed to discuss the special unit. Several officials became agitated when asked about the functions of the ISA unit.

"No, no and no," Justice Ministry spokesman Moshe Cohen told Israeljustice.com.

During the March 2005 session, Mr. Nitzan and other officials provided details of the secret intelligence unit. They said the unit was meant to determine whether dissent or civil disobedience constituted incitement or sedition, punishable by five years under Israeli law.

"We are very sensitive to crimes called ‘crimes of expression,’" the ISA legal adviser said. "The treatment is different from that of other crimes because there is a thin line between freedom of expression and criminal acts. These include incitement to violence, incitement to racism, and incitement to draft evasion."

Over the last year, about 700 people were indicted in connection with the protest campaign against the Israeli withdrawal from the Gaza Strip and northern Samaria, officials said. Several of the indictments pertained to newspaper articles or letters critical of officials who directed the withdrawal.

Officials said the prosecution has handled what they termed clear cases of incitement or sedition. The new ISA unit, they said, was reserved for what one official termed "clandestine matters."

The intelligence unit was also granted extensive powers, officials said. This included the use of agents to infiltrate the anti-withdrawal movement, comprised mostly of Jewish teenagers.

"We call them live sources," the ISA legal adviser said of the agents. "This is no secret, and if it is a secret, I’m revealing that we operate live sources to collect information in problematic situations."

During the hearing, the intelligence official acknowledged the unauthorized use of an agent-provocateur to incite the man who eventually assassinated then-Prime Minister Yitzhak Rabin in 1995. The official said the agency has "come a long way" since ISA handled the agent, Avishai Raviv.

The legal adviser said ISA has been cooperating with the Justice Ministry and the attorney general in the use of agents against Jewish dissidents. He said the agency also operated a so-called Jewish division, which monitored those deemed Jewish extremists.

For his part, Mr. Nitzan told the Knesset session that the ISA unit was meant to help authorities block the rise in anti-withdrawal protests. He said the state prosecutor drafted guidelines to confront incitement and sedition.

"The prosecutor’s office is already overloaded," Mr. Nitzan said. "As a result, there are cases that it is important to deal with quickly to send a message to prevent additional violations of the law. We’ve also asked for more judges."

During the session, several committee members expressed concern over the new unit. Knesset member Yuli Edelstein, imprisoned in the 1980s as a Jewish dissident in the Soviet Union, said he was worried by the ISA use of agent-provocateurs, employed widely in totalitarian countries.

"The angle that really worries me is the activity of the agents," Mr. Edelstein said. "We need to supervise the Justice Ministry."

Other committee members expressed concern over the authority of the secret intelligence unit to comb the media and Internet sites for dissent. Knesset member Yitzhak Levy said this was unprecedented in Israel.

"Justice Minister Tzipi Livni said the unit will go through newspapers every day and try to spot [negative] remarks," Mr. Levy said. "It seems that we are speaking about an activism that is above and beyond what is usually discussed."

Today, several of the committee members said they no longer receive updates regarding the ISA unit. But attorneys who represent anti-withdrawal activists said the unit’s activities were adopted by other agencies in the law enforcement community.

"People in the police are doing this," Yitzhak Klein, director of the Jerusalem-based Israel Policy Center said. "They have a computer crimes section and they are looking for incriminating material and there is some evidence that these cases are run through Mazuz himself. It’s possible that we see here one of the outcomes of the special unit."

Knesset committee members said Mr. Eitan was the sole liaison between Israeli authorities and parliament concerning the government campaign against anti withdrawal opponents. But even during the 2005 hearing, Mr. Eitan doubted whether parliament could maintain oversight over the ISA unit.

"There are gray areas like everything in life, but the Justice Ministry is on top of things," he said. "It could be that we in the Knesset need to supervise the Justice Ministry and receive information. But even then, there will be things that are not right. What can we do? Should we get rid of these operations that we know we need?"