Israeli airstrikes killed a civilian and two Palestinian militants in the Gaza Strip on Monday as mutual hostilities in the Middle East continued to escalate, medical sources said. 

The latest strike comes after four days of attacks that began Friday when an Israeli strike killed two suspected militants accused of planning a cross-border attack via Egypt.

At least 21 people had died in Gaza as Israel's campaign entered its fourth day, following reports of three more killings on Monday, including that of a 15-year-old boy, according to Palestinian officials. 

The BBC reported that at least 65 people have been wounded in Gaza since Israel's bombardment began.

Israel is not keen to see an escalation, Israel is not keen to hurt innocents  -- Israel is absolutely opposed to this, said Interior Minister Eli Yishai, a member of Prime Minister Benjamin Netanyahu's eight-member inner council.

For now, [fighting] is on this kind of scale. But if it will prove protracted, then without a doubt there will be a powerful, painful blow will be so that this will not continue, he told Israel's army radio.

According to the leadership of Hamas, which governs the Gaza Strip, mediators from neighboring Egypt were working on a cease-fire Sunday night, with the Israelis agreeing to a midnight halt to the fighting.

But Islamic Jihad -- an Iranian-backed faction who claimed to be responsible for most of the rocket fire -- intensified attacks overnight, according to the Associated Press.

At least 28 other Palestinian civilians have been wounded since Friday, Reuters reported, with two dozen, including several children, wounded in a predawn strike Monday in Gaza City.

Israel has closed schools in the south of the country in a bid to avoid further casualties.

The latest clashes between Israel and Gaza militants are the bloodiest in months, but both Israel and Hamas seem keen to avoid the all-out-war that erupted three years ago, claiming thousands of lives.

Fearful of such a retailation, Hamas has been eager to distance itself from the latest rocket attacks, despite Israel holding it ultimately responsible for any launches emanating from the areas it controls.