“That people in Germany are threatened and abused because of their Jewish appearance or their support for Israel is an outrageous scandal that we won’t accept,” Ms. Merkel said. “It’s our national and civic duty to fight anti-Semitism.”

Jews from across the country traveled to the capital by the busload to take part in the demonstration that many viewed as an important chance to show their solidarity with Israel, as well as publicly acknowledge their religion. Some Jews say they have been discouraged from wearing outward symbols of their religion in public in recent months as a safety precaution.

Beyond the anti-Semitic demonstrations, Molotov cocktails were thrown at a synagogue in the western city of Wuppertal and Jewish cemeteries were desecrated.

Hedva Lüttge, a teacher from Israel who has lived in Germany for 20 years, said that on the way to Sunday’s demonstration, four pro-Palestinian supporters began shouting at her and her friends, until the police intervened. Hundreds of police officers were in place for the demonstration, which took place without any incident, apart from some heckling by bystanders over Israel’s policies in the Middle East.

Armin E. Husung said he had encountered anti-Jewish sentiments in the course of his career as a lawyer and notary in Berlin. He came to the demonstration, with his partner and his 11-year-old son, because “I wanted to show clearly which side I am on,” Mr. Husung said.