The New Israel Fund filed a police complaint on Monday after several suspects broke into their Jerusalem offices and tampered with their signs.

The New Israel Fund's signs have been tampered with twice before, and sources in the NIF believe the rightist group Im Tirtzu is responsible for the acts.

Rachel Liel of the NIF said that her group has been dealing with virtual attacks on its Web site over the past few days. She said that she and NIF President Naomi Chazan, who has been depicted in an advertisement with a horn on her head, also receive threatening emails and phone calls.

"The e-mails I received were calls to stop us, to shut our mouths…. Very violent e-mails," said Liel.

"As someone who lived here and experienced the days before the murder of Yitzhak Rabin and Emil Grunzweig, we take these threats seriously. We began locking the doors, and we will install security cameras and complain to the police," Liel added.