Concerned that terrorists may strike ahead of this weekend's Purim holiday, the IDF began on Tuesday to impose a full closure on the West Bank and the Gaza Strip slated to remain in effect until Sunday. Defense Minister Ehud Barak decided on the closure following a security assessment he held Tuesday morning with representatives of the IDF, Shin Bet (Israel Security Agency) and Israel Police. Police Insp.-Gen. Dudi Cohen has also ordered the police to beef up security in public areas over the weekend. During the security assessment, Barak was presented with intelligence that terrorists might attack Israeli cities over the holiday weekend. Police will deploy thousands of officers and volunteers at holiday celebrations as well as at bus stations and malls throughout the country. On Tuesday, three Kassam rockets struck the western Negev without causing any injuries or damage. In the evening, the IDF and the Shin Bet targeted an Islamic Jihad cell involved in recent Kassam fire against Sderot, in the northern Gaza village of Beit Lahiya. Palestinians said that five people were wounded by the strike. The increase in the level of alert also comes after threats from Hizbullah, which the defense establishment fears will carry out an attack in the coming days to avenge the assassination of the group's operations chief Imad Mughniyeh in Damascus on February 12. Israel has denied involvement in the killing. Mughniyeh's 40-day mourning period will end this weekend. The Shin Bet has also decided to dramatically increase its level of security surrounding Israeli embassies, consulates and other offices overseas, and to beef up security and alter some arrangements for El Al Israel Airlines flights. One of the main concerns is that terrorists will try to down an Israeli passenger jet with a shoulder-to-air missile, as al-Qaida tried to do in Kenya in 2002. The IDF Northern Command and UNIFIL have also raised their level of alert on both sides of the Lebanese border in case Hizbullah tries to carry out an attack in the North. Israel has reportedly sent the message to Hizbullah that it would respond strongly to any aggression in Israel or abroad.