The Israeli military said at least 68 rockets and mortars struck southern Israel on Wednesday, damaging homes and wounding several foreign laborers working in fields near the Gaza border.

It said the barrage began late Tuesday with several other rockets hitting Israeli territory. Israeli authorities closed schools in the border area as a precaution.

Israel carried out a series of retaliatory air strikes on Gaza late Tuesday and Wednesday, killing four Palestinians, including three members of the Hamas militant group that controls Gaza. The strikes also wounded several Palestinians.

Hamas and a smaller militant group called the Popular Resistance Committees claimed responsibility for the rocket attacks on Israel, saying they were a response to Israeli aggression.

Early Tuesday, militants also set off a bomb along the Gaza-Israel border fence, wounding an Israeli soldier. Israeli Prime Minister Benjamin Netanyahu vowed a strong response to that attack.

Hamas members accused Israel of seeking revenge on Gaza for hosting a brief visit by the emir of Qatar earlier Tuesday. It was the first by a head of state to Gaza since Hamas seized power there in 2007. The militant group said the Qatari emir’s visit was a victory in its efforts to end its political and economic isolation.

The Gaza-Israel border has seen occasional outbreaks of fighting between militants and Israeli forces since the two sides fought a brief war from December 2008 to January 2009.