The Israeli military on Thursday warned people to evacuate a city and other communities in southern Lebanon that are north of a UN-declared buffer zone, signaling that it may widen a ground operation launched earlier this week against the Hezbollah militant group.

Israel has told people to leave Nabatieh, a provincial capital, and other communities north of the Litani River, which formed the northern edge of the border zone established by the U.N. Security Council after the 2006 war in a resolution that both sides accuse the other of violating.

The fighting has driven nearly 1.2 million people from their homes in Lebanon, the country's crisis unit said Thursday.

At least nine Israeli soldiers have been killed in clashes with Hezbollah in southern Lebanon, where Israel announced the start of what it says is a limited ground incursion earlier this week. The fighting comes as the region braces for Israel's response to an Iranian ballistic missile attack.