Israeli forces and Hezbollah militants exchanged fire across the Israel-Lebanon border on Saturday in a second day of hostilities after the collapse of a truce in Gaza between Palestinian group Hamas and Israel.

Iran-backed Hezbollah said in a statement that one of its fighters was killed but did not specify when. Three people in south Lebanon were killed by Israeli shelling on Friday in south Lebanon, according to Lebanon's state news agency. Hezbollah said two of the dead were its fighters.

Hezbollah also said it fired rockets at an Israeli position. Israel's military said two mortar bombs launched from Lebanon fell in open areas in Shomera, across the border from the south Lebanon village of Marwahin. The military said it responded by attacking the launch site and elsewhere in south Lebanon.

Earlier on Saturday, shelling from Israel hit close to the United Nations Interim Force in Lebanon (UNIFIL) headquarters near the coastal town of Naqoura and around the border village of Rmaych, a UNIFIL spokesperson said.

The Israeli military said it carried out shelling near Naqoura after spotting "unusual activity" in the area.

UNIFIL also detected fire around 11 a.m. (0900 GMT) from the area of Tayr Harfa, about a mile from the Israeli frontier, toward Israel, the spokesperson said.