A blast on Lebanon's border with Israel wounded two Israeli soldiers on Tuesday and the Israeli army responded with shelling across the frontier, a military spokeswoman and a security source said.
The security source earlier said three troops were hurt in the incident, which took place near the southern Lebanese village of Kafr Shebaa.
Lebanon's Al-Manar television, which is aligned with the Shi'ite militia group Hezbollah, said an explosion had been heard in the area. Officials in Beirut had no immediate comment.
Israel and Lebanon are technically at war but their 80 km (49 mile) border has been largely quiet since a month-long war between Israeli forces and Hezbollah in 2006.
Israel remains on alert for any spillover from the civil war in neighbouring Syria, where Hezbollah forces are fighting in support of President Bashar al-Assad.
On Sunday, the Israeli military said it fired on two people who tried to slip into the country from Lebanon. Both turned back, the military said.