Police reported that two men in a car cut off a minivan carrying a rabbi and eight rabbinical students in Berlin early Sunday and repeatedly shouted anti-Semitic slurs before throwing a burning object at the vehicle.
In a separate incident, vandals overturned 17 gravestones at a Muslim cemetery in the northern city of Hamburg late Friday, daubed Stars of David on several and draped others with a sheet emblazoned with a Nazi swastika, authorities said.
"Investigators' first impression was that this anti-Semitic/xenophobic act against Muslims was apparently committed by ignorant people with no knowledge of politics and was unique in its kind," Hamburg police said in a statement.
The Berlin office of the American Jewish Committee condemned the incidents in a statement.
"We denounce anti-Semitic attacks and any aggression against religious dignitaries and sites and call upon authorities to do their utmost to find and prosecute the perpetrators of such heinous crimes," the head of the office, Deidre Berger, said.
Berger quoted data from the German interior ministry reporting more than 500 anti-Semitic crimes in the first half of the year, amounting to nearly three per day.
She said the prevalence of such offences made clear that the German government needed a special ombudsman to deal with anti-Semitism.
A proposal for parliament to approve the appointment of an official responsible for coordinating the government's response to anti-Semitism as part of a motion on the Kristallnacht anniversary has failed to win a majority.
Deputies from Chancellor Angela Merkel's conservative Christian Democratic Union have called instead for a committee of experts to draw up regular reports on anti-Semitic incidents.
With ceremonies throughout the country Sunday, Germany will mark the 70th anniversary of the Night of Broken Glass, or Kristallnacht, when Nazi thugs rampaged against Jewish citizens on November 9-10 of 1938, torching synagogues and vandalising Jewish-owned businesses.
Historians consider the pogrom to have been a harbinger of the Holocaust in which six million European Jews were systematically slaughtered by the Nazis during World War II.