The border clashes were the most serious in months and came a day after a veteran Hezbollah commander was killed in a Beirut car bombing. Hezbollah blamed Israel (search) for the assassination. Israel denied any role in the bombing.
The security officials, who declined to be named, said an Israeli tank opened fire on a Hezbollah position near the border town of Aita el-Shaab, killing a Hezbollah guerrilla. A Hezbollah spokesman confirmed the death of the guerrilla but gave no details.
The guerrillas returned fire at Israeli positions across the border, in turn drawing Israeli helicopter fire, the officials said.
Israel confirmed airstrikes and a firefight in the area but said the clashes began when Lebanese snipers fired on an Israeli border post. Israel Army radio described the Lebanese fire as "precise," indicating Israeli casualties.
Israeli forces withdrew from southern Lebanon after an 18-year occupation in May 2000, but cross-border skirmishes continue.
Israel and the United States considers Hezbollah a terrorist organization. It is widely regarded as a liberation movement throughout the rest of the Middle East.