Sirens warning of rocket fire from Gaza cut short an election rally by Israeli Prime Minister Benjamin Netanyahu in the southern city of Ashkelon late Tuesday, public television reported.
KAN 11 broadcast footage of Netanyahu's security detail closing in around him as he was speaking from the podium.
One them whispered in his ear before the premier raised a hand in farewell and was hustled from the building.
The Israel army said in a brief statement that sirens had sounded in Ashkelon and the port city of Ashdod, but it did not elaborate.
There were no immediate reports of rockets falling in any urban area.
The incident came less than three hours after Netanyahu pledged to annex the Jordan Valley in the occupied West Bank if re-elected in September 17 polls.