(JTA) — Israeli security officials are increasingly concerned about the threat of large-scale terror attacks by ISIS. In an article Dec. 19, Haaretz reported that Israel’s “defense establishment” believes a growing number of Arab-Israelis are joining the Islamic extremist group, and that ISIS branches on the Syrian border with the Golan Heights and in Egypt’s Sinai will recruit Arab-Israelis to commit terror attacks. The Israel Defense Forces also said ISIS operatives just north of the Israel-Syria border may be planning attacks on Israel, according to the Times of Israel. In particular, the IDF said it is concerned about the possibility that the Shuhda al-Yarmouk group of ISIS fighters there will send an explosives-packed vehicle over the border, fire anti-tank missiles and rockets, or plant explosive devices along the border fence. In response, Israel has stepped up security along the fence.

Over the weekend, the Iraq- and Syria-based Islamic terrorist group, which has not previously targeted Israel, threatened attacks against “the Jews in Palestine” in an audio tape reportedly made by ISIS leader Abu Bakr al-Baghdadi.

According to Haaretz, several Arab-Israelis have been found with ties to ISIS in the past year.