The flare-up between Hamas and Israel began on Sunday night when Israeli special forces began a land operation into Gaza. 

Hamas vowed revenge after seven Palestinians, including a top Hamas commander, were killed. One Israeli soldier was killed and another wounded in the raid.

Israeli warplanes pounded targets in the densely populated Gaza Strip on Monday, while Palestinian militants fired hundreds of mortars and rockets in the fiercest exchange of fire since the 2014 war.  

Read more: Israeli raid in Gaza leaves several dead, including IDF soldier and Hamas commander

The Israel Defense Forces (IDF) said on Monday evening they had struck more than 30 militant sites in response to more than 300 rocket and mortar launches from Gaza fired following the Israeli undercover raid on Sunday night. Hamas and Islamic Jihad claimed credit for the rocket launches. 

Lt. Col. Jonathan Conricus, an IDF spokesman, said the army had sent reinforcements to the Gaza frontier and bolstered its Iron Dome missile defense system.

"We continue to strike and retaliate against the military targets belonging to terrorist organizations in Gaza, and as for our intentions we will enhance these efforts as needed," he told reporters.

The IDF said they had struck Hamas' military intelligence headquarters, claiming the group had "intentionally established their HQ next to a school."

Hamas accused Israel of "deliberate targeting of civilians and civilian facilities" in one of the most densely populated places in the world. 

The Gaza health ministry said at least three Palestinians, including two militants, were killed in the Israeli strikes. 

A 19-year-old Israeli soldier was in a critical condition after military bus in southern Israel was hit by an anti-tank missile, the IDF said.  Later, a man was killed when a rocket hit a building in southern Israel. 

Among the Israeli targets was Hamas' Al-Aqsa TV building in Gaza, which was destroyed after a series of warning shots were given for journalists to clear the building. The IDF accused the station of broadcasting "incitement and violence for years."

"Tonight, the IDF made sure that this station won't broadcast again," the army said. 

Hamas said in a statement that the demolishing of Al-Aqsa TV was an attack on the press and "reflects the Israeli occupation’s murderous mentality and exposes all its atrocious crimes, terror acts, and abhorrent violations against the Palestinian people."  

In 2010, the US Treasury listed Al-Aqsa TV as a specially designated global terrorist. 

'Back from the brink'

The escalation of violence has threatened to upend weeks of UN and Egyptian-led diplomacy to reach a long-term ceasefire between Israel and Hamas.

UN Middle East envoy Nickolay E. Mladenov said his office and Egypt were working to bring Gaza "back from the brink."

"The escalation in the past 24hrs is EXTREMELY dangerous and reckless. Rockets must STOP, restraint must be shown by all!" he wrote on Twitter. 

Just before Sunday's Israeli raid in Gaza that triggered the latest escalation, Prime Minister Benjamin Netanyahu said that he was striving to reach a long-term ceasefire with Hamas rather than a new war.

"This is happening at a delicate juncture in Hamas-Israeli relations," Hugh Lovatt, a regional expert at the European Council on Foreign Relations, told DW. "The two sides are attempting to come to a longer-term arrangement that can preserve calm in exchange for an easing of socio-economic conditions within Gaza."

Hamas armed wing accused Israeli forces on Sunday of having "infiltrated this evening in a civilian car" and assassinating a top commander. Israel had stressed the operation was an intelligence-gathering mission and "not intended to kill or abduct terrorists, but to strengthen Israeli security."

Blow to ceasefire talks, humanitarian situation

Netanyahu has come under criticism from members of his right-wing government for his decision to allow Qatar to provide money to the Hamas-run Gaza Strip to pay for salaries and provide other support to ease a humanitarian crisis in the coastal enclave. 

Last week, Qatar delivered $15 million (€13.2 million) of cash in suitcases to the Gaza Strip. The payment was part of $90 million that Qatar has pledged to deliver to cover the salaries of thousands of employees in the Gaza Strip in the next six months.

The immediate impact of the Qatar payment was for Hamas to ease border protests on Friday. Since March 30, thousands of Palestinians in the Gaza Strip have gathered at weekly protests along the Israeli border to demand a lifting of an Israeli-Egyptian blockade and an improved humanitarian situation.

More than 200 Palestinians have been killed and thousands injured by Israeli forces during the Gaza protests in the past seven months, according to the enclave's health ministry. One Israeli soldier has been killed. 

Israeli Education Minister Naftali Bennett, the head of the right-wing Jewish Home party, likened the cash payments to the Gaza Strip as "protection money" paid to criminals. Hardline Defense Minister Avigdor Lieberman said he had opposed "transferring the money to Hamas."

Israel and Hamas have fought three wars since 2008, but both sides have signaled that they want to avoid another full-scale conflict.

 cw/jm (AP, dpa, Reuters)

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