JERUSALEM—As southern Israel was barraged by rockets for a fourth straight day, Prime Minister Benjamin Netanyahu said Israel was hitting back “strongly and decisively,” and its Iron Dome anti-missile defense system was intercepting many of the rockets coming from the Gaza Strip.

“The IDF is continuing to—strongly and decisively—attack the terrorists in the Gaza Strip,” Netanyahu said Monday at the Knesset. “Whoever intends to harm our citizens, we will strike at him.”

Israel has responded to the barrage of missiles with more than 30 attacks on rocket-launching sites and weapons facilities. At least 20 Palestinians, including two civilians, have been killed since the recent violence began. Several dozen Palestinian civilians, including several children, reportedly have been wounded in the strikes.

More than 200 rockets have been fired at Israel since Israel assassinated a terrorist leader from the Popular Resistance Committee. Israel’s military said the PRC leader, Zuhir Mussah Ahmed Kaisi, was planning an attack on Israel through the Sinai.

At least eight Israelis have been injured, two seriously, in the attacks by the PRC and Islamic Jihad. Hamas, which rules Gaza, has not launched missiles in the latest round of attacks.

At least two dozen rockets were fired from Gaza into Israel on Monday. The Iron Dome system intercepted at least eight fired at Beersheba and five at Ashdod.

One rocket fired Monday struck an empty kindergarten building, a day after a rocket landed in a school courtyard. One rocket Monday struck Gadera, located 24 miles south of Tel Aviv.

Also Monday, rockets fired from Gaza struck the Kerem Shalom crossing between Israel and Gaza, which has remained open throughout the hostilities. The crossing was closed for about half an hour before operations were continued. A truck and a van on their way to deliver goods to Gaza were hit, according to a statement by Israel’s coordinator of government activities in the territories.

“Despite the continuous barrage of mortars and artillery shells from the Hamas-run Gaza Strip, the IDF and COGAT continue to honor Israel’s commitments to transfer goods through the Kerem Shalom crossing to the people of Gaza in an efficient and secure manner,” the statement said. 

Schools were closed for a second day on Monday in cities and towns located up to 25 miles from the Gaza border, affecting about 200,000 children. Classes at colleges and universities in the area also were closed.

United Nations Secretary-General Ban Ki-moon said Monday that he is “very concerned” by the new round of violence, saying that civilians on both sides are paying a heavy price. 

Netanyahu said Sunday that Israel remains on alert against an attack from Sinai. The prime minister commended the security and intelligence services in the airstrike that killed Kaisi and another member of the Popular Resistance Committee.

“We have exacted from them a very high price,” he said. “Naturally we will act as necessary.”

Netanyahu praised the Iron Dome missile defense system, which according to the IDF has intercepted 90 percent of its targets.

“We will do everything in our power to expand the deployment of this system” in the months and years ahead, he said.

Netanyahu also lauded the residents of the southern Israeli communities for their resilience in the face of the rocket barrage. He met Sunday with with 30 municipal leaders from the area and received their staunch backing.

“In the end, the strongest force at our disposal is the fortitude of the residents, of the council heads, of Israelis and of the government,” he said.

On Sunday afternoon, a rocket that landed in a residential neighborhood of Beersheba damaged 15 homes; another rocket that landed near a Beersheba school caused damage to the structure. Pieces of a rocket intercepted by Iron Dome also hit a car and a water pipe in the city, according to Ynet.

The United States said it was “deeply concerned by the renewed violence in southern Israel,” U.S. State Department spokesman Victoria Nuland said in a statement issued Saturday. “We condemn in the strongest terms the rocket fire from Gaza by terrorists into southern Israel in recent days, which has dramatically and dangerously escalated in the past day. We call on those responsible to take immediate action to stop these cowardly acts.

“We regret the loss of life and injuries, and we call on both sides to make every effort to restore calm,” the statement concluded.

Egypt’s ambassador to the Palestinian Authority, Yasser Othman, told the Palestinian Ma’an news agency Sunday that Egypt was working to halt the escalation of violence between Gaza and Israel. He said his country was in contact with both sides in an attempt to stop the violence in order to “to avoid undesirable developments.”

Othman called Israel’s offensive “unjustifiable and a breach to the truce sponsored by Egypt.”

The Popular Resistance Committees promised revenge for Kaisi’s assassination.

“All options are open before the fighters to respond to this despicable crime,” said Abu Attiya, a PRC spokesman. “The assassination of our chief will not end our resistance.”

It is believed that the short-range rockets are being launched by the Popular Resistance Committee, according to the IDF, while the long-range and midrange rockets are being launched by Islamic Jihad.

Palestinian Authority spokesman Nabil Abu Rudaina said that “Israel’s escalation creates a negative atmosphere and increases the tension, which leads to the increase in violence in the region,” according to CNN.

The IDF issued a statement saying that it holds “Hamas responsible for the recent incidents since the terror organization currently has jurisdiction in the area [Gaza].” The statement said that “The Hamas movement, although not the one performing the launchings, is not doing anything to prevent it either.”