Four Israeli soldiers were wounded when an explosive device went off at the border with Lebanon near Rosh Hanikra.
They were airlifted to an hospital in Nahariya for surgery.
An Israel Defence Forces (IDF) spokesman said the soldiers were involved in "an activity near the border" and didn’t elaborate further.
Andrea Teneti, a spokesman for UNIFIL, the UN peacekeeping force in southern Lebanon, 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.
Israeli Prime Minister Benjamin Netanyahu said Israel would "continue to act responsibly" to defend its borders.
Daily newspaper Yisrael Hayom wrote about the incident : "The action was carried out in a place where Israel did not want to be caught," in order to forestall some hostile activity, most likely by Hezbollah.
A senior IDF officer said Wednesday that "Hezbollah's involvement in the war in Syria has not disrupted its preparedness for a war with Israel – the opposite is true."
Colonel Yaron Formosa, the chief artillery officer of the IDF's Northern Command, told the Ynet news website that Hezbollah gunmen have become proficient in the use of advanced weapons due to the fighting in Syria.
He stressed that despite Hezbollah's heavy losses in Syria, the Lebanese Shiite group’s lookouts are constantly monitoring IDF activity along the border. "We saw them marking the positions of our artillery guns so they can target them in a war. As a counter measure we are building embankments to protect the weapons and ammunition."
"They are continuing to prepare for a war against us, and an isolated incident on the border can lead to deterioration. We are prepared to go to war even tomorrow morning," he said.
He said most of the rocket-launching pads the IDF would attack in case a war breaks out have been moved from open areas to villages in southern Lebanon. "It is difficult to operate in an urban setting. For many Lebanese it will be intolerable. Hezbollah may purposely prevent the civilians from fleeing to the north," he said.
"But Hezbollah has tens of thousands of rockets that are aimed at Israel, and we will not be able to operate against them only with artillery fire or the air force. We will need a ground maneuver as well."