BEIRUT (AP) - The leader of Hezbollah has refused to comment on a Bulgarian report that said members of the Lebanese militant group carried out an attack that killed five Israeli tourists in the European nation. Sheik Hassan Nasrallah says the "issue is being followed calmly and carefully." Speaking to hundreds of supporters via video link, Nasrallah warned Israel Saturday not to attack Lebanon, saying Hezbollah's response will be harsh. The July 18 bombing killed the five Israelis as well as a Bulgarian bus driver and the suspected bomber at the airport in the Black Sea resort of Burgas. Three men are suspected in the attack, including the bomber. The latter's identity has not been established. The names of the two other suspects, believed to still be alive, have not been made public.