Israeli jets have struck in southern Lebanon during a day of escalating tension on the Israeli-Lebanese border.
Israeli jets are often accused of violating Lebanese airspace
The raid came after anti-aircraft rounds were fired at Israeli jets which were violating Lebanese airspace.
The warplanes responded by attacking suspected hideouts of the guerrilla group Hezbollah, security sources said.
Last year the UN criticised the Israeli air force for intrusions over southern Lebanon. Israeli forces left Lebanon in 2000 after 22 years of occupation.
Lebanese officials quoted by Associated Press said two Israeli fighter jets fired missiles at a valley near the village of Zibqine, southeast of the port city of Tyre.
Black smoke was seen coming from the area. There was no information about possible casualties.
Military sources in Israel said anti-aircraft shells fired by Hezbollah had landed on the Israeli side of the border hitting a collective farm and beach.
A small fire started in a wooded area but there were no casualties.
The United Nations expressed "great dismay" at the exchange of firepower.
"One violation cannot justify another," a UN envoy said in a statement, which urged "Israel to halt its overflights and the Lebanese side to halt the ensuing and dangerous anti-aircraft fire".
The last time Israeli aircraft were in action over Lebanon was on 23 March, when helicopter gunships fired on suspected guerrillas preparing to fire a rocket.
The border area has been predominantly peaceful since Israel withdrew its forces in 2000 after the long and bloody occupation.
However, Hezbollah fighters have repeatedly clashed with troops in the disputed Shebaa Farms area, which they consider Lebanese land still under Israeli occupation.
The border is mainly peaceful now
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 Israel has occupied since 1967.
Lebanon has repeatedly complained to the United Nations about Israeli reconnaissance flights that violate its airspace.
Israel accuses Hezbollah of deliberately targeting its territory in the guise of anti-aircraft fire in order to terrorise populated areas.
The rise in tensions comes as German mediators were reportedly negotiating with Israel and Hezbollah to complete the second stage of a prisoner swap begun in January.
Hezbollah is expected to supply information about an Israeli airman missing in action to secure the release of a Lebanese militant jailed in Israel.