JERUSALEM, July 15 (Xinhua) -- Israel's military said Sunday it had retaliated several mortar bombs fired from Gaza at its territory, a few hours after a ceasefire between Israel and Hamas was announced.

A military spokesperson said that overnight four mortars were fired into southern Israel, and the Iron Dome defense system intercepted at least one of them.

"In response, the IDF (Israel Defense Forces) struck the mortar barrels from which the mortars were launched," the spokesperson said.

However,these incidents occurred even though a ceasefire was achieved on Saturday. Both the Islamic Hamas movement and the Islamic Jihad announced on Saturday night that the efforts exerted to reach an agreement with Israel on getting back to calm and end escalation in the Gaza Strip "had succeeded."

On Sunday morning, the Israeli Home Front Command told residents of the southern communities near Gaza that they can "return to normal." Over the weekend, they were instructed to stay indoors or within a short range of shelters.

The calm came shortly after two Gaza children were killed and more than 40 wounded in the intensive Israeli war plane airstrikes waged on the Gaza Strip since Friday night.

Israel hit Gaza with over 40 airstrikes while Gaza militants launched at least 100 mortar bombs at Israel, according to official Israeli figures.

Israel on Saturday attacked a high-rise building in the al-Shati refugee camp, which according to the army has been used as a training facility for urban warfare for Hamas. It also carried out a large strike on a Hamas Battalion headquarter in Beit Lahia in the northern Gaza Strip, the spokesperson said.

Gaza militants have also sent "burning kites and helium balloons" to southern Israel's arid farmlands, and at least 32,000 dunams (32 square km) of farmland and forest were razed by "fire from the sky," according to official figures.

The escalation came amidst weekly rallies near the fence separating between Israel and the Palestinian enclave. The mostly-peaceful demonstrators protested the crippling blockade imposed by Israel and Egypt in 2007.

Israel charges that the protest had been orchestrated by Hamas, the Islamist Palestinian movement that runs the Gaza Strip.