An explosion at the border with Lebanon wounded four Israeli soldiers on Wednesday, and the Lebanese Army said the troops were inside Lebanese territory when the blast occurred.
The incident, in an area known for having land mines, did not appear to herald any surge in tension along a frontier that has been largely quiet since Israel and Lebanese Hezbollah guerrillas fought a war in 2006.
An Israeli military spokesman said the soldiers were involved in "an activity near the border". He did not provide details about their exact location or what caused the blast.
Four soldiers were wounded and taken to hospital in Israel, the spokesman said.
The Lebanese Army said that in a "violation of Lebanese sovereignty", an Israeli infantry patrol crossed the U.N.-designated "blue line" between the two countries and moved 400 meters (yards) inside Lebanese territory.
"During the infiltration, an explosion occurred which led to a number of (Israeli soldiers) being wounded," the Lebanese military said, adding it was investigating the circumstances of the blast in coordination with U.N. peacekeepers in southern Lebanon.
A Reuters reporter in Lebanon who visited the scene saw blood on an asphalt road.
Commenting on the incident, Israeli Prime Minister Benjamin Netanyahu said Israel would "continue to act responsibly" to defend its borders.
Andrea Teneti, a spokesman for the peacekeeping force, UNIFIL, described the situation along the frontier after the explosion as calm.
In a statement, UNIFIL said it had opened an investigation and had asked the Israeli military to provide details "of any incident in the area as alleged" and its precise location.