A federal grand jury indicted Alexandria Police Chief Charles T. Strobel yesterday on charges of perjury and obstructing justice, capping a yearlong investigation into allegations of wrongdoing in the city's police department.

The 12-count, 67-page indictment alleges that Strobel lied to the grand jury during his appearances before it in October and December by saying he could not remember certain events when questioned about his handling of allegations of sexual wrongdoing by other police officers.

Strobel, 48, who has headed the police force since September 1977, said he would not comment on the indictment other than to say he was disappointed.

City Manager Vola Lawson said she immediately placed Strobel on administrative leave with pay pending resolution of the charges. She named Deputy Chief Arlen Justice acting chief.

Strobel's attorney, David G. Fiske, said, "I think it's ridiculous that after . . . months of looking at charges that supposedly span 13 years they are unable to come up with any substantive charges and instead rely on these allegations of false statements."

Lawson and Mayor James P. Moran Jr. were in Richmond with other city officials when informed of the indictment. Moran said they would return immediately to Alexandria and go directly to City Hall to read the indictment.

"I think it has to be emphasized that an indictment is not a finding of guilt," said Moran. "It is purely a matter of one grand jury determining that another jury should be empowered to find guilt or innocence."

Strobel's indictment is a major twist in a long-running controversy among city officials about the way he has run the police department.

A year ago, a special Alexandria grand jury cleared him of wrongdoing in a drug probe unconnected with the matters that are the subject of the federal indictment. But even that report favorable to the chief figured prominently in the City Council elections last spring. The controversy over Strobel became so bitter that City Manager Douglas Harman, who had backed Strobel, left his job in disgust and took a similar post in Fort Worth.

The indictment charges that Strobel, when he testified before the grand jury on Oct. 23 and Dec. 12, made false declarations and obstructed justice by testifying that he could not remember some events.

According to the indictment, Strobel was brought information, including taped conversations, in 1974 and again in 1978 concerning allegations that an Alexandria police officer had attempted to have sexual relations with a prostitute who had become a police informant. Strobel was also told that two Fairfax County vice squad police officers had arrested the prostitute under false pretenses and were having sexual relations with her, the indictment states.

Strobel, the indictment states, ordered the persons who brought him these allegations, Alexandria police officers Louis Pugh, John Miller and Larry Brohard, to cease any investigation into the matter.

Questioned about this by the grand jury, Strobel repeatedly said, "I do not recall," according to testimony attached to the indictment.

No one was charged by Alexandria police in connection with the allegations that according to the indictment were brought to Strobel's attention.

The indictment also states that in 1973 and 1975, when he was a captain in command of the police department's internal affairs section, Strobel received information that the same Alexandria officer had attempted to rape two women. He did not pursue the allegations at the time he received them and "filed a false report" of the 1973 incident, the indictment states.

But when asked last fall about receiving the allegations, Strobel said he could not recall if or when he had heard them, according to the indictment.

If convicted, Strobel could be sentenced to up to 60 years in prison and fined up to $90,000.

The special Alexandria Circuit Court grand jury that cleared Strobel last February of wrongdoing in an unconnected matter criticized unnamed City Council members for "callous, politically motivated" actions that it said attempted to damage Strobel's reputation.

Moran, a former vice mayor, used the issue in his successful challenge to then-mayor Charles E. Beatley in elections last May.

Moran held a press conference during his mayoral campaign to say that Beatley, an outspoken critic of Strobel's management of the department, should apologize to Strobel -- and added that he himself would issue an apology if the federal innvestigation found any wrongdoing.

Reminded of that pledge last night, Moran said, "I have always felt that criminal charges should be considered through the judicial process and I object vehemently to a public trial in the press."

Former city councilman Donald C. Casey, another critic of Strobel, was defeated along with Beatley in the election.

Casey said last night he felt vindicated. "It took the feds to clean up a mess we could have cleaned up in Alexandria except for the perfidy of commonwealth's attorney John Kloch and certain council members," he said at the federal courthouse just after the indictment was returned. Kloch, the Alexandria prosecutor, said a year ago he had reviewed the local grand jury's decision and found it accurate.

Kloch could not be reached last night.

Strobel's difficulties in the past year, in addition to the two grand jury probes, included a $15,000 punitive damages judgment ordered by a federal judge in a suit brought by two police officers. The officers accused Strobel of violating their civil rights by transferring them from detective duties to foot patrol. The city's insurance paid the judgment.

As Alexandria's public safety director for 27 months, Strobel headed firefighting and code enforcement functions, as well as the police force. Last month, Lawson dismantled the Public Safety Department, which had been plagued by morale and other problems. Strobel was retained as police chief without loss of any of his $72,000 annual salary.

City officials who could be reached last night were unanimous in expressing surprise at Strobel's indictment.

"I am just in shock and I can't imagine anybody feels any different," said City Council member Redella S. Pepper. "I can't believe it happened."

Wiley F. Mitchell, the city's state senator, said, "It's astonishing news. I am sure most people in the city would say the same thing."

Assistant U.S. Attorney Justin Williams, who led the grand jury investigation, which heard more than 30 witnesses over the past year, told U.S. District Judge Richard L. Williams he would arrange a date for Strobel's arraignment today. Prosecutor Williams was assisted by Peter George, a member of the Justice Department's Public Integrity Unit, during the investigation.