Hizbullah has launched an investigation into Sunday's rocket attack on Kiryat Shmona in an effort to discover who fired the Katyushas, a high-ranking UNIFIL officer told The Jerusalem Post on Monday. According to the officer, it was still unclear who was behind Sunday's firing of two Katyusha rockets into Israel. On Monday, a previously unknown group calling itself "the Jihadi Badr Brigades - Lebanon branch," claimed responsibility for the attack. "We affirm that we will continue no matter what the sacrifices on the jihad path are," said the statement, which began with a Koranic verse and carried a picture of Jerusalem's Dome of the Rock with a Palestinian flag in the background. The growing assessment within the Israeli defense establishment was that a terror cell affiliated with al-Qaida was behind the rocket fire, although the possibility that the attack was perpetrated by a Palestinian group with ties to Hamas was also being investigated. Khaled Aref, a senior official with the mainstream Palestinian Fatah movement in the southern Lebanon refugee camp of Ein el-Hilweh, said he had no knowledge of the group. He said Palestinians had agreed not to use south Lebanon to attack Israel because "we don't want to put more pressure on Lebanon." Israeli defense officials said Hizbullah's decision to launch its own independent probe into the attack was an attempt to further distance itself from the attack out of fear of an aggressive Israeli retaliation. On Sunday, Hizbullah issued a statement claiming that it was not involved in the rocket attack. The UNIFIL officer rejected criticism by the IDF that the peacekeeping force should have prevented the attack, claiming that even "100,000 peacekeepers were not capable of preventing a couple of people from firing a crude rocket." According to the Kuwaiti Al-Siyasa newspaper, Syrian President Bashar Assad was behind the Katyusha rocket attack. The paper claimed that Assad's motive was his anger at the Arab League foreign ministers' positions during last week's Cairo summit, particularly the stances of Egypt and Saudi Arabia, who called for an end to Syrian involvement in Lebanon. According to the newspaper, Assad reacted harshly to the criticism, saying: "They will see how I will plough up Lebanon." Meanwhile, in northern Lebanon on Monday, three Lebanese soldiers were killed in the latest fighting of a five-week siege against a terror group barricaded inside a Palestinian refugee camp. Their deaths brought to 72 the number of Lebanese soldiers who have died in the battle with Fatah al-Islam at the Nahr el-Bared camp. AP contributed to this report.