Israeli warplanes have attacked sites near the Lebanese village Kfar Shouba in the disputed Shebaa Farms region.
The Israeli-Lebanese border has seen a week of firing
The Israeli raid came after fighters from the Lebanese Shia militia, Hezbollah, and Israeli troops shelled each other across the border.
These are the latest exchanges in a week of cross-border firing.
Israeli missiles struck positions near Kfar Shouba and helicopters hit a suspected Hezbollah post just inside the Lebanese border, witnesses said.
There were no casualties from the Hezbollah fire, an Israeli military spokesman said. There was no immediate word on casualties on the Lebanese side from the Israeli fire.
The Israeli military said Hezbollah positions opened fire on Israeli outposts in the Shebaa Farms.
Hezbollah's al-Manar television said the attack was in retaliation for Israeli attacks on Lebanese territory, including a hit on civilian houses in the village of Kfar Shouba.
This is the heaviest clash between Israel and Hezbollah since January, when Hezbollah guerrillas blew up an Israeli bulldozer operating in Shebaa Farms and Israeli warplanes retaliated with strikes that wounded two Lebanese women.
Hezbollah fighters occasionally attack Israeli forces in the Shebaa Farms area, which is nestled near the Israeli, Lebanese and Syrian borders.
Hezbollah says the Shebaa Farms area is occupied Lebanese territory - but Israel, backed by the UN, says the farms are on the Syrian side of the border and so are part of the Golan Heights, which it has occupied since 1967.