French police were investigating a previously unknown Islamic militant group's claim of responsibility for an arson attack on a Jewish community center, a spokesman said Monday.

The official at Paris police headquarters said it was still unclear whether the posting on a Web site known for militant Islamic comment by a group calling itself Jamaat Ansar Al-Jihad was a serious claim.

Authorities immediately suspected the fire at the center in eastern Paris was deliberately set. The blaze broke out before dawn Sunday, and no one was hurt. The center is used as a meeting place and soup kitchen.

When the smoke cleared, investigators found anti-Semitic graffiti and swastikas scrawled in red marker.

One message read, "Without the Jews, the world is happy," while another said, "Jews get out."

The message that appeared Sunday on the Web was unusual.

The message said that "a group of Mujahedeen youth set fire at 4 a.m. Paris time to the Jewish synagogue in Paris in retaliation for the racist acts carried out by the Jews in France against Islam and Muslims, and acts of defiling Muslims' cemeteries."

The posting, which referred incorrectly to the community center as a synagogue, said the blaze marked the 35th anniversary of a fire at al-Aqsa Mosque in Jerusalem, which gutted the southeastern wing of the holy shrine.

Rumors quickly spread of Israeli responsibility, though a non-Jewish tourist from Australia confessed to setting the fire. He was hospitalized in a mental institution and later deported from Israel.