With western security agencies on high alert for a possible Hizbullah terror strike next week to mark the end of the 40-day mourning period for Hizbullah's senior military commander Imad Mughniyeh, sources in Jerusalem noted an odd Syrian silence about progress into an investigation into his killing. According to assessments in Jerusalem, the fact that neither Syria, Iran or Hizbullah have come out since their initial reflexive accusations against the Mossad with any statement linking Israel to the attack indicates that the Syrians may have "embarrassing" information linking the killing to the Arab world. The assessments noted that the same silence followed the Israeli bombing of a military installation in Syria in September, with Syria - following some initial statements on the matter - keeping a near complete silence on what was attacked. Some foreign reports said the target was a nuclear installation. According to these assessments it was abnormal for Syria, a number of weeks after it announced an investigation, not to trot someone out saying he acted on behalf of Israel. This silence has led to a number of theories, including that the Syrians found evidence of involvement by other Arab countries, or even the involvement of Syrian agents, that would acutely embarrass the regime or damage Syria's relations with other Arab states. According to assessments in Jerusalem, it is likely Syria will only release information of its investigation into the Mughniyeh killing after the Arab League summit in Damascus later this month, in order not to antagonize any neighboring Arab states who might be implicated and would then work to derail the conference. The Shin Bet (Israel Security Agency) has decided to dramatically increase its level of security surrounding Israeli embassies, consulates and other offices worldwide out of fear that they may be targeted by Hizbullah in conjunction with the end of Mughniyeh's 40-day mourning period. Officials said that it was possible that Syria and Iran might assist Hizbullah in perpetrating the attack and has also decided to beef up security and alter some arrangements for El Al Airlines flights around the world. One of the main concerns is that terrorists will try to down an Israeli passenger jet with a shoulder-to-air missile like al-Qaida tried to do in Kenya in 2002. Yaakov Katz contributed to this story.