The head of the local office of the Anti-Defamation League of B'nai B'rith called on religious and government leaders yesterday to help protect area synagogues from what he said is "an alarming increase" in anti-Semitic incidents, ranging from vandalism to bomb threats.

Edward N. Leavy, director of the ADL's D.C.-Maryland regional office, made the appeal after an incident Monday night in which vandals spray-painted anti-Semitic "murals" on the walls of Shaare Tefila Synagogue in Silver Spring. According to Leavy, it was the fourth incident of vandalism at a synagogue in the Washington area in the last month.

He called on Mayor Marion Barry, the governors of Maryland and Virginia and the leaders of other religious bodies to join in "efforts to protect area places of worship, especially those which seem to be targets of extremist attacks, like synagogues."

Leavy cited statistics to reflect the increase of anti-Semitic incidents both locally and nationwide. In Maryland, reported incidents increased from fewer than 10 in 1980 to 51 in 1981. No anti-Semitic incidents were reported in the District of Columbia in 1981; there have already been 7 in 1982.

National figures gathered by the ADL showed that such episodes "increased substantially in 1981," the third straight year an increase was registered, according to Leavy.

Jewish leaders say that statistics do not accurately reflect the true extent of such incidents, since there is a great reluctance on the part of many victims to report such acts for fear of encouraging their repetition. Rabbi Joshua Haberman of the Washington Hebrew Congregation, acknowledged with some reluctance that vandals had painted "some kind of inscription" on the wall of the Northwest Washington synagogue earlier this year.

"I do not perceive it as a threat," said the rabbi, who came to this country as a refugee from Nazi Germany. "Vandalism has increased all over the country."

Marshall Levin, executive director of Shaare Tefila, said the red spray-painting on an unlighted wall "looks more professional than anything seen before in Montgomery County." He characterized it as five separate "murals," involving such symbols as swastikas, skull and crossbones, the Christian cross and the sword, "all in perfect proportion."

Levin said Shaare Tefila leaders had decided that rather than removing the inscriptions immediately, they would "use them to educate as many as possible . . . who will come to look, especially members of our congregation and of the community and our young people, so they can deal with these acts of hatred."

He said other religious leaders in the area had expressed sorrow over the incident. "It will be discussed from the pulpits this weekend," he said. Members of Christian churches will join with Shaare Tefila members on Sunday, he said, to clean the walls.

Montgomery County Executive Charles Gilchrist, who surveyed the scene at Shaare Tefila Tuesday, said yesterday he was "really horrified. It's just so professional in a horrifying way." He said that in addition to the police, the county's Human Relations Task Force, formed last year to deal with such problems, is also investigating the matter.