The UN says a peacekeeper has been killed in Lebanon amid border clashes between Lebanese militant group Hezbollah and the Israeli army.
The UN urged "maximum restraint" from all parties to avoid further escalation.
Four Israeli soldiers were injured when an anti-tank missile hit an army vehicle in the disputed Shebaa Farms area, military officials said.
The Israeli army responded by firing shells into southern Lebanon.
The Israel Defence Forces said on Twitter that initial reports suggested that an anti-tank missile was fired at a military vehicle near Mt Dov.
Israeli Prime Minister Benjamin Netanyahu tweeted: "At this moment the IDF responds to events in the North. We will not allow terrorists to disrupt the lives of our citizens and threaten their security. We will respond forcefully those who try to challenge us."
Israel has ruled out the abduction of any troops.