Although the number of police on the Cambridge force is at a historic low, violent crimes have decreased by 13 percent in 1992, according to a city report released yesterday.

Numbers for all categories of crime were down over the last year except for drug related arrests, which increased by 12 percent from 185 in 1991 to 207 in 1992.

Murders are down from five to two. The largest crime category is larceny, down slightly from 3,363 to 3,326.

There were 872 violent crimes reported in Cambridge in 1992 and 5079 property crimes

The report called "the telephone being used as a weapon of terror" the most disturbing crime trend of 1992 Telephone threats and harassment soared from 400 incidents in 1990 to more than 900 in 1992, the re port said.

The crime rates have steadily decreased for the last three years because of more strategic police assignments, Cambridge Police Commissioner Perry L. Anderson said.

He also attributed the improvement to the recent focus on drug-related crimes and neighborhood-oriented policing.

"The actual [drug] arrests have increased while the incidents have gone down," Anderson said.

Despite the advances on crime, the department will add 38 officers by June.

Residents and city officials said they were wary of the positive report. The murders of an MIT student and a Boston youth late last year touched off a wave of community concern and activism.

"We don't want to convey the message that everything is okay and we can rest on our laurels," said William Lee, co-chair of the Area Four Crime Task Force, a neighborhood watch group.

Forty percent of the 1992 drug arrests took place in Area Four, according to the report. Area Four is located between Central Square, Inman Square and MIT and is bordered by Prospect Street, Mass. Ave. and Hampshire Street.

"Crack cocaine is now the driving force and product of choice on the streets," the report said.

Cyr Criticizes

Councillor Edward N. Cyr warned that the statistics can be misleading because they are a "false measure of the impact of crime on a community."

"There were people on Washington Ave. who said a good part of 1992 children were sleeping under their beds because someone was going around shooting a 22-caliber pistol," Cyr said.

Anderson said he was pleased with the statistics but that the police will continue their efforts because "we still have 500 plus victims."

"We would like to see a 50 percent decrease," he said