The Lebanese military says its anti-aircraft guns opened fire Wednesday at an un-manned Israeli aircraft that flew over southern Lebanon.
There were no reports that any Israeli plane was hit.
However, it was the first time Lebanese forces fired at Israeli planes since last year's war between Israel and Lebanon's Hezbollah guerrillas.
Israeli planes regularly fly reconnaissance missions over Lebanon, despite protests from the Beirut government and repeated appeals from U.N. peacekeepers in the region to halt the practice.
Israel's military chief says Hezbollah is trying to re-arm after last year's month-long war.
Speaking during Israeli military exercises on the Golan Heights, Lieutenant General Gabi Ashkenazi said Israel may have to take steps to deal with Hezbollah.
Both Ashkenazi and Israeli Prime Minister Ehud Olmert say that Hezbollah has not regained its pre-war strength.
After the war, Lebanon deployed about 16,000 troops in the southern part of the country, where Hezbollah guerrillas had been in control. More than 12,000 U.N. peacekeepers also are in the region monitoring the ceasefire.
Israel says the over-flights are necessary to ensure that Hezbollah guerrillas do not smuggle weapons into the country's southern region along the Israeli border.
In other news, the Israeli military announced it had destroyed a cave used by Hezbollah before the war on the Israeli side of the border with Lebanon.
And the U.S. Treasury Department announced Wednesday that it has designated the construction arm of Hezbollah as a terrorist organization.
Some information for this report was provided by AFP, AP and Reuters.