The pro-Syrian terror organization Hizbullah on Tuesday accused the UN team investigating the assassination former Prime Minister Rafik Hariri of passing on crucial intelligence on Lebanon's security to Israel. The accusation appeared to be part of a campaign to discredit the inquiry amid mounting tension between Lebanon and Syria. Syrian President Bashar Assad sharply criticized Lebanon's prime minister in a speech last week, calling him a "slave" to the West. In Damascus, some 300 children aged 6 to 10 held a sit-in demonstration along with their parents in central al-Rawdah Square, protesting international pressure on Syria connected to the probe as the government attempted to rally the public behind it. "We are children. We came here out of love," read a banner carried by the demonstrators. Assad's government has been under heavy pressure since the UN Security Council unanimously demanded last month that it cooperate fully with the probe into Hariri's death in a Feb. 14 bomb blast in Beirut. The council warned of further measures if Syria fails to cooperate. A UN report last month implicated top Syrian and Lebanese security officials in the bombing. Syria has denied any role in the killing. Syria's UN ambassador said Tuesday that his government opposes investigators' demands to question six senior Syrian officials in Beirut, though he said it was willing to hold their questioning elsewhere. Until now, Hizbullah officials avoided criticizing the UN investigation led by German prosecutor Detlev Mehlis. But on Tuesday, the head of Hizbullah's 11-member bloc in parliament sharply criticized the probe, accusing it of exposing Lebanon's security secrets to the Mossad intelligence agency. "The security files held by the military establishment in Lebanon have now come into the hands of the Mossad," Raad said in an interview with the TV channel New Television on Tuesday night. "Mehlis has 120 investigators of various nationalities and no one in Lebanon had checked their background," he said. "All files of internal security, communications and intelligence have been opened under the pretext of investigation. We don't know who photocopied these files and to whom they were sent," he said. "The Israelis have become acquainted with everything relating to our national security." Raad did not present any evidence of information being passed to Israel and could not be reached by The Associated Press for further comment. Hizbullah has in the past accused Israel of seeking to intervene in Lebanon's internal affairs and has said an Israeli role in Hariri's assassination should not be ruled out. The Iranian-backed group wields great influence and has a wide popular base within Lebanon's 1.2 million-strong Shiite community, the country's largest sect. Hizbullah, labeled a terrorist organization by the United States and Israel, led a guerrilla war against Israel's 18-year occupation of a border zone in southern Lebanon that ended in 2000. Hizbullah's stepped up attack against the UN team followed a tough speech by Assad targeting the investigation and the new Lebanese government, which is dominated by anti-Syrians.