The exchange of fire came hours after US President Joe Biden visited Israel and the occupied West Bank.

"A short while ago, IDF fighter jets struck a military site in the central Gaza Strip belonging to the Hamas terrorist organisation," a statement from the Israel Defense Forces said.

"The military site consists of an underground complex containing raw materials used for the manufacturing of rockets.

"The strike on this site will significantly impede and undermine Hamas' force-building capabilities," it said, adding that Israel was responding to "attacks from the Gaza Strip on Israeli territory".

During the night there had been two separate launches, each of two rockets, towards Israeli territory, the military said.

Warning sirens alerting residents to the rocket fire had sounded during the night in the city of Ashkelon and elsewhere in Israel's south.

Israel's military said one of the rockets had been intercepted while the other three fell on empty land.