He said it was unclear whether the new front was "symbolic or something more substantial."
Lebanon's state-run National News Agency said two rockets were fired Friday from the country. No one immediately claimed responsibility for the attack.
Gaza militants already have fired more than 400 rockets against Israel in the offensive. Israel's "Iron Dome" defense system has intercepted most aimed at major cities. Air raid sirens sounded once more Friday across the country, including for the first time in the northern city of Haifa.