A counterterrorism project in Los Angeles that would collect information about Muslim neighborhoods is drawing outrage from Islamic groups and civil libertarians who say it unjustly singles out residents based on faith and could lead to unconstitutional police tactics.

The groups complain that the Los Angeles Police Department's "community mapping" project, which aims to prevent radicalization and homegrown terrorism, unfairly brings suspicion on Muslims.

They say it undermines trust established between Muslims and police since the 9/11 attacks and is reminiscent of how Nazis identified Jews during the Holocaust.

"This is anti-Semitism reborn as Islamophobia," said Shakeel Syed, director of the Islamic Shura Council of Southern California. "We will fiercely resist this."

The mapping project would collect information about specific neighborhoods but not individuals, according to Michael Downing, the LAPD's counterterrorism chief.

Downing said the aim is to study where enclaves of Muslims live so that police can study their culture, history, language and socioeconomic status to gain an understanding of their communities.

If a community is isolated, it may be determined that it is susceptible to extremist ideology, Downing said.

In such cases, he said, police could then go into those communities and try to head off potential problems by offering people access to government and social services.

"Our goal is to try to be a catalyst to integrate the communities into the greater society," he said.

How much information would be collected and how it would be used remained unclear to groups such as the American Civil Liberties Union, which joined Muslim groups in writing a harshly worded letter earlier this week to the LAPD.

"Singling out individuals for investigation, surveillance and data-gathering based on their religion constitutes religious profiling," the letter said. "In addition to constitutional concerns ... religious profiling engenders fear and distrust."

Darrel Stephens, president of the Major Cities Chiefs Association, said large police departments routinely use community mapping to understand crime trends.

Muslim leaders say mapping based on a community's faith and ethnicity is different from mapping based on crime.

"In the Muslim community, there hasn't been terrorism," said Hussam Ayloush of the Los Angeles chapter of the Council on American-Islamic Relations.

Ayloush said the police department's job is to enforce laws. "Police should not be in the business of analyzing political views and religious views," he said. "It's really dangerous. This is a slippery slope."

The ACLU agreed.

"Religious profiling is not a legitimate tool of law enforcement," said Ranjana Natarajan, an attorney with the ACLU of Southern California.