At least four people, among them three foreign agricultural workers, were wounded and at least seven homes sustained serious damages in southernIsraelWednesday, as Palestinians fired dozens of rockets and mortars into Israel overnight and early in the morning.

Two of the foreign workers, reportedly Thai working at a chicken coop, sustained critical wounds; another of the injured is a border policeman, according to the first responders.

The rockets and mortars struck some areas in the Eshkol Regional Council, Sha'ar Hanegev and the Ashkelon coast.

The Iron Dome missile defense system intercepted seven rockets heading toward Ashkelon, according to a spokesman of the Israeli Defense Forces (IDF).

Home Front Command and municipal authorities cancelled schools across a swath of southern Israel within the range of the long- range Grad, and shorter-range Kassam rockets.

"In lockdown. Constant barrage on the region," read a warning text message sent to residents in affected areas.

The army said Israel Air Force (IAF) craft have flown out on at least four sorties overnight in efforts to supress the Gazan salvos.

"In response to the rocket fire, IAF aircraft targeted a rocket launching site in the northern part of the Gaza Strip. In addition, tank shells were fired towards terrorist targets in the Gaza Strip, " the Spokesman's Office said in a statement sent to Xinhua.

"Over 67 rockets were fired from the Gaza Strip toward southern Israel over the past eight hours," the army said.

Israeli airstrikes killed three Palestinian militants in Gaza Tuesday evening and early Wednesday morning, Palestinian medical sources told Xinhua.

"There's no doubt that this will lead to an escalation," Defense Minister Ehud Barak said in an interview with Army radio. He cautioned that "all options are open."

Ezz el-Deen al-Qassam Brigades, the armed wing of Gaza's Hamas rulers, claimed responsibility for firing the rockets together with the Popular Resistance Committees (PRC), a militant group with close ties to Hamas.

The Israeli army says that it "will not tolerate any attempt to harm Israeli civilians, and will operate against anyone who uses terror against the State of Israel."

Israeli Prime Minister Benjamin Netanyahu Tuesday vowed that his government is ready to give a "very, very hard" response to a militant bombing attack against the army.

After nearly three weeks of airstrikes aimed at suppressing attacks from Gaza, the Israeli army says the fighting may yet get worse before it subsides.