Israeli Prime Minister Benjamin Netanyahu said he has ordered “massive strikes” in the Gaza Strip after a two-day escalation that killed nine Palestinians and three Israelis.

“This morning I instructed the IDF (Israel Defense Forces) to continue with massive strikes against terrorists in the Gaza Strip,” Netanyahu, who doubles as Israeli defence minister, said in a statement after consulting with his security cabinet on Sunday.

“I also instructed that forces around the Gaza Strip be stepped up with tank, artillery and infantry forces,” Netanyahu added, stoking fears of a ground invasion into Gaza.

The new hostilities, which first broke out on Friday, flared on Sunday, with Palestinians fleeing Israeli raids in Gaza and air-raid sirens sending Israelis running to shelters as interceptor missiles blew up rockets from Gaza in the sky.

Israeli media reported Gaza fighters over the past two days fired more than 400 rockets at towns and cities in southern Israel and that the Israeli Iron Dome anti-missile system had intercepted more than 250 of them.

The government media office in Gaza said Israeli warplanes carried out about 150 raids, in addition to artillery-shelling targeting 200 civilian landmarks in the Gaza Strip, including residential buildings, mosques, shops and media institutions.

About 40 Palestinians were wounded in the attacks, according to Gaza’s health ministry.

Israel has waged three offensives on Gaza since December 2008.

The last war in 2014 severely damaged Gaza’s already weak infrastructure, prompting the United Nations to warn that the strip would be “uninhabitable” by 2020.