UNITED NATIONS (AFP) - UN Secretary-General Antonio Guterres appealed Sunday (May 5) for "maximum restraint" after Israel launched retaliatory strikes in Gaza for rocket fire from the Hamas-controlled territory.

"He condemns in the strongest terms the launching of rockets from Gaza into Israel, particularly the targeting of civilian population centers," a UN statement said.

"He urges all parties to exercise maximum restraint, immediately de-escalate and return to the understandings of the past few months," it said.

Guterres's special envoy Nickolay Mladenov was "working closely with Egypt and all concerned to restore calm," the statement said.

Israel carried out waves of retaliatory strikes in Gaza on Sunday after Palestinian rockets hit cities in Israel.

Gazan authorities reported at least 16 Palestinians killed, while Israel said four people were killed in the rocket attacks from Gaza.