Israel’s Counter-Terrorism Bureau on Wednesday warned Israelis against traveling to Tunisia over concerns that jihadist terrorists may try to attack the visitors or Jewish targets in the North African country.

In a statement the CBT said that, following a situation assessment, “it was decided to further reiterate the severe travel advisory for Tunisia.”

The warning was issued ahead of an annual pilgrimage that draws hundreds of Tunisian Jews and visitors from Israel to the island of Djerba, where they celebrate at an ancient synagogue believed to be the oldest in Africa.

“Terror elements, with a focus on global jihadist elements, continue their efforts to carry out an attack against various destinations in Tunisia,” the CBT said. “Given the gravity of the threat, the Counter Terrorism Bureau advises Israelis to refrain from visiting the country and those who are there to leave immediately.”

The traditional festive procession near the El Ghriba synagogue on Djerba takes place on or around Lag B’Omer, a minor Jewish festival between Passover and Shavuot. The celebration this year begins on May 14 and continues into the following day.

Last year the bureau, a branch of the Prime Minister’s Office, put out a similar warning against traveling to Tunisia for the festival. The event went ahead amid tight security from Tunisian forces, although many stayed away, reducing the numbers from the thousands who have attended in the previous years.

The synagogue, in the village of Hara Seghira, or Er-Riadh, dates back to 586 BCE, although the current building was reconstructed in the 19th century. In 2002, terrorists blew up a vehicle near the synagogue, killing 21.

Agencies contributed to this report.