The Israeli army announced this on its Twitter page.

“The air-raid sirens sounded in the kibbutz Nahal-Oz and the kibbutz Alumim,” the report said.

הופעלה התרעה בקיבוצים נחל עוז ועלומים. הפרטים בבדיקה

- צבא ההגנה לישראל (@idfonline) February 1, 2020

According to the Israeli military, the alarm was triggered by the fact that the system recorded the launch, presumably of missiles, from the territory of the Gaza Strip in Israel.

Earlier, the Israel Defense Forces stated that a rocket was fired from Gaza across Israeli territory. Later, Israeli troops fought back.