JERUSALEM — Gaza's militant Hamas rulers threatened to escalate fighting with Israel on Saturday after airstrikes killed several gunmen in the coastal territory, and Palestinian rocket attacks on Israel wounded one person and damaged an elementary school in the country's south.

The two sides periodically clash, but this flare-up was the most serious in months. It started with an attack by a little known al-Qaida-inspired Palestinian militant group but has extended to drag in Hamas.

Hamas has largely stayed out of direct confrontation with Israel since a war more than three years ago although other factions have launched cross-border attacks.

Gaza militants fired over 30 rockets and mortar shells on Saturday alone, bringing the week's rocket tally to more than 150, according to the Israeli military.

Over a million people in southern Israel live in range of the rockets and the Israeli military has advised the residents to make sure they can get to a bomb shelter quickly.

An Egyptian official in Ramallah said that he is trying to broker a cease-fire between the Palestinian militant groups and Israel. He said he hoped calm would be restored by late Saturday. Egypt traditionally plays a mediating role between the sides.

The official spoke on condition of anonymity because negotiations were ongoing. Israel had no immediate official comment on the Egyptian efforts, but Hamas official Ayman Taha said his group would cease fire if Israel does. Soon after Taher spoke more rockets fired from Gaza exploded in southern Israel. It was not clear which group fired them.

A previous cease-fire reached late Tuesday did not hold long.

Military Chief of Staff Lt. Gen. Benny Gantz convened "an urgent meeting" to discuss ways of dealing with a week of persistent Palestinian attacks, a spokesman said, while Defense Minister Ehud Barak consulted with senior officials Saturday evening. There was no official statement afterward but the Israeli media reported that the decision was made "to meet fire with fire and quiet with quiet."

Israel's military said it carried out a series of airstrikes Saturday in response to the rockets. At least four militants were killed and over 20 Palestinians, both combatants and civilians, were injured, according to Gaza health official Ashraf Al Kedra.

Hamas' military wing, the Izzedine al-Qassam Brigades, vowed to escalate the fighting.

"If the last rounds were not enough to deliver the message ... we are ready to crush the enemy and to curb its arrogance and to respond to aggression in a strong way," the group said in a statement released Saturday afternoon.

A few hours later an Israeli airstrike killed a Gaza militant riding a scooter. The Popular Resistance Committees, a Hamas-allied militant group that often fires rockets at Israel, said he was a member. Witnesses said the force of the explosion caused a wall of a nearby building to collapse, injuring several people. The Israeli military said they targeted the militant as he was preparing to launch rockets.

In an earlier attack the same day, an Israeli airstrike killed a Palestinian militant as he rode his motorcycle in Gaza. Several buildings used by Hamas, which rules the coastal territory, were also damaged.

The Israeli military said it hit "terror sites" and that it holds Hamas accountable for any attacks originating from the Gaza Strip.

Also, an Israeli was seriously wounded when a Gaza rocket smashed through a factory roof. Rockets from Gaza also hit a school in the Israeli border town of Sderot. The school was closed for the weekend so no one was hurt but the building was damaged. Several other Israelis were injured in Palestinian rocket attacks this past week.

"We have been enduring years of relentless Palestinian escalations and this is just one of them," said David Buskila, mayor of the Israeli border town Sderot where the school was hit. "We trust the Israeli military and government to restore calm," he said.

The spike in violence began Monday when two gunmen infiltrated into Israel along its border with Egypt's Sinai peninsula and killed an Israeli Arab construction worker who was part of a crew building a border security fence meant to avert such attacks. Later, a little known al-Qaida-inspired group, the Mujahedeen Shura Council of Jerusalem, claimed responsibility for the attack and identified the gunmen as an Egyptian and a Saudi.

Since then, Gaza gunmen have fired barrages of rockets and mortar rounds at Israel, wounding several Israelis and damaging apartment buildings. Israel has carried out airstrikes on militant targets that killed at least 12 Palestinians and wounded dozens so far.

Meanwhile, Gaza health official Ashraf Al Kedra said a boy was killed in a playground during an airstrike Saturday morning in Khan Younis. The Israeli military said it had not attacked that area.

Military spokeswoman Lt. Col. Avital Leibovich later called the allegation a "false rumor" and said that according to intelligence information, the boy was killed by "ordinance belonging to one of the terror groups." Palestinian rockets often misfire and explode inside Gaza.

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  • A fireman extinguishes a fire at al-Saraya Security complex in the centre of Gaza City on June 23, 2012 as Israel launched fresh air strikes on the Gaza Strip overnight after killing two people in earlier raids. (MAHMUD HAMS/AFP/GettyImages)

  • Palestinian mourners carry the body of Hamas militant Hamam Abu Qadus during his funeral in Gaza City on June 23, 2012 as Israel launched fresh air strikes on the Gaza Strip overnight. (MAHMUD HAMS/AFP/GettyImages)

  • A Palestinian man inspects the damage at al-Saraya Security complex in the centre of Gaza City on June 23, 2012 as Israel launched fresh air strikes on the Gaza Strip overnight after killing two people in earlier raids. (MAHMUD HAMS/AFP/GettyImages)

  • A wounded security police officer is seen on the ground following an Israeli air strike on the building in Gaza City, early Saturday, June 23, 2012. (AP Photo/Yasser Qudih)

  • Palestinian medics wheel a wounded man to the treatment room of Al-Aqsa hospital following an Israeli airstrike east of Bureij refugee camp, in Deir Al Balah, central Gaza strip, Friday, June 22, 2012. (AP Photo/Ashraf Amra)

  • Young Palestinian relatives of Basel Ahmed mourn during his funeral in the al-Bureij refugee camp in the central Gaza Strip on June 22, 2012 after he was killed and two were wounded, one seriously, when Israeli warplanes struck east of Al-Bureij. (SAID KHATIB/AFP/GettyImages)

  • Palestinians sit outside a hospital in the al-Bureij refugee camp in the central Gaza Strip on June 22, 2012. (SAID KHATIB/AFP/GettyImages)