Israelis are being urged to avoid Sinai in the coming months as a number of Palestinian terrorist cells are believed to have infiltrated the area with advanced plans to strike at Israeli tourists, officials from the Counter-Terrorism Bureau warned on Tuesday. The warning came a day after the bureau revealed that two attempts by Hizbullah to kidnap five Israeli businessmen overseas were recently foiled by Israeli security services. The plots were also in the advanced stages and defense officials said Tuesday that Hizbullah would continue trying to attack Israelis in retaliation for February's assassination of the group's military commander Imad Mughniyeh in Damascus. "Hizbullah means business and is in the midst of a number of plans to retaliate for Mughniyeh's death," a defense official said. Regarding Sinai, defense officials said the warning issued by the Counter-Terrorism Bureau was more severe than those issued in the past. The defense establishment traditionally issues travel advisories ahead of holidays. Rosh Hashana begins on the evening of September 29. "The threat in Sinai is real," a senior Defense Ministry official said. "Israelis should not travel there and those who are there should immediately return home." Jerusalem fears that terrorist cells have used the current cease-fire with Hamas in Gaza to infiltrate Sinai and search for Israelis to either kidnap or murder. Israel is also concerned with the possibility that a large number of Gazan terrorists may have crossed into Sinai over the weekend after Egypt opened the Rafah border crossing for two days. Egypt said it opened the border on Saturday as a gesture to Palestinians before Ramadan, which began on Monday. Hamas officials in Gaza said Sunday that about 2,500 people had crossed into Egypt since the crossing was opened.