Anti-Semitic incidents in affluent Montgomery County are getting more violent and account for about 75 percent of all reported racial violence in the county, officials said this week.

But the officials also said police are making more arrests and legislators at the county and state level are considering laws that would separate racially motivated violence from other forms of assault and vandalism.

Statewide, Maryland had more incidents of ethnic or religious violence reported in 1984 than the previous year, but not as many as in 1982, according to data collected by police and local human relations panels.

The Coalition Opposed to Violence and Extremism, a watchdog group, said there were 421 incidents in Maryland last year of harassment or violence against people because of their religion, race or cultural background. That compares with 356 in 1983 and 505 in 1982.

About 150 incidents of vandalism or assaults on Montgomery County's Jewish community were reported each year for the past three years, said Alan Dean, director of the county Human Relations Commission.

County police Sgt. Richard Williams said reports of violence against Jews account for 75 percent of all reported ethnic violence.

The latest incident in Washington's Maryland suburbs was reported Sunday night, the eve of the Jewish New Year, when vandals painted an obscene message on the wall of the Oseh Shalom temple in Prince George's County.

The Anti-Defamation League of B'nai B'rith said there have been twice as many incidents of anti-Semitic activity as there has been anti-black activity this year. The rate of violence against blacks and Jews has been about the same during the last two years, ADL spokesman David Friedman said.

The incidents have become more violent in recent months, including cross-burnings and physical attacks, Dean said.

"One reason synagogues are such an easy target is because of their accessibility," Dean said, pointing to clusters of Jewish houses of worship along 16th Street in Silver Spring and Old Georgetown Road in Bethesda.

There are about 120,000 Jews in metropolitan Washington, and Montgomery County has the highest concentration, Friedman said.

More citizens are reporting racially motivated violence, Dean said, adding: "In previous years, people just didn't think it was important and the police wrote it off as general vandalism, but all that has changed."

Dean said both the county and state legislatures are considering laws that would separate vandalism perpetrated against ethnic groups from general vandalism and increase the penalties for ethnic-related crimes. Officials said such a bill will be reintroduced in next year's session of the Maryland General Assembly.

In Maryland, 151 incidents of racial or religious harassment were counted by the Maryland Human Relations Commission during the first five months of this year.

Melvin Mintz, cochairman of the coalition, said he could not explain the increase in such events as cross-burnings, swastika paintings and related assaults. Though there were more incidents in 1982 than in the following two years, Mintz said, "the feeling is that the violence in those acts is increasing."

Nationally, fewer incidents of harassment have been recorded in recent years, but ethnic-related assaults have increased, said Joan C. Weiss, executive director of the Baltimore-based National Institute Against Prejudice and Violence, created this year by Gov. Harry Hughes with the help of $200,000 in state funds.

Weiss said data on anti-Semitic incidents collected nationally by the Anti-Defamation League indicates Maryland ranks third in such incidents. Mintz said anti-Semitic incidents in Maryland rose from 55 in 1982 to 73 in 1984.