The fourth-century Hamat Tiberias Synagogue was desecrated Monday night by vandals who sprayed graffiti on the walls and tore up the mosaic floor. The Israel Antiquities Authority suspects extremist ultra-Orthodox Jews who say the authority damages ancient graves during excavations.

The vandalism was discovered yesterday morning by employees of the Israel Nature and Parks Authority.

Similar acts have been carried out at other archaeological sites; one slogan sprayed Monday night read "A site for every grave [desecrated]." Another read "For Shuka," probably referring to Shuka Dorfman, the head of the antiquities authority.

One employee burst into tears yesterday when viewing the vandals' work. "Afghanistan is right here," another added.

Tiberias police are investigating the case, while the authority is trying to tally the damages and figure out if anything can be restored.

The synagogue, in Hamat Tiberias National Park, was discovered in 1921 by writer and translator Nahum Slouschz. It was uncovered in the first major archaeological dig led by Zionist Jews in the Holy Land.

"The most beautiful part of the mosaic from the fourth century was severely damaged," said Dror Ben Yosef of the antiquities authority. "The perpetrators drilled a hole in the drawing of the holy ark and damaged the menorah drawing as well. It seems they worked very hard trying to take apart the floor."

A zodiac wheel drawn on the mosaic appears to have been hit by a pickax. "There are Haredim who believe that if a zodiac wheel is drawn there, it can't really be a synagogue," Ben Yosef told Haaretz. "The zodiac wheel, in this case, is actually a judaized Helenistic motif." One corner of the mosaic was completely taken apart.

Ben Yosef added that the synagogue was "probably the site where the Jerusalem Talmud was completed" and that the mosaic contained important symbols such as a holy ark with an ornamental curtain, along with a menorah, a shofar, a ceremonial palm frond and a coal pan.

The mosaic included inscriptions in Hebrew, Aramaic and Latin. Ben Yosef said extremist Haredim have threatened other sites. "We'll protect the sites," he said. "Whoever vandalized it desecrated its holiness. These people damaged our historic heritage."

Dina Avshalom-Gorni of the antiquities authority said conservation and restoration work would be carried out, but this wouldn't be enough.

"It will never be the same mosaic that people prayed on 1,600 years ago," she said. "You can feel and learn here how people once lived, prayed, studied and talked. It will never be the same. We're facing a vandalist drive against heritage sites that's gaining momentum. Something has to be done to stop it."

In the past two months several other archaeological sites have been damaged. A mosaic was vandalized at Hurvat Hanut near Jerusalem, a 1,300-year-old furnace was damaged near Yavneh, and a container holding artifacts was set on fire in Afula.

"Public servants who safeguard our historical heritage have also been threatened recently," Avshalom-Gorni added. "It's definitely a frightening situation."