Story highlights Israel carries out airstrikes against nearly three dozen targets in Gaza

"It's just too sad to even imagine," victim's aunt tells CNN

"Hamas will pay" for the deaths, says the Israeli Prime Minister

Hamas spokesman warns against escalation

Tensions between Israel and Hamas ratcheted up Monday after the bodies of three Israeli teenagers, kidnapped this month, were found in the West Bank.

Israel, in no uncertain terms, blames the disappearances and deaths on Hamas.

"Hamas will pay," said Israeli Prime Minister Benjamin Netanyahu.

Hamas spokesman Sami Abu Zuhri warned against escalation, saying that if Netanyahu "brings a war on Gaza, the gates of hell will open to him."

The three bodies were found northwest of Hebron, according to the Israeli military, which said they were still in the process of being identified.

The teens -- Eyal Yifrach, 19; Gilad Shaar, 16; and Naftali Frankel, a 16-year-old dual U.S.-Israeli citizen -- disappeared late June 12 or early June 13 from the Jewish settlement of Gush Etzion in the West Bank, the military said.

"Although the identification has not been officially confirmed, I would like to send my support and condolences to the Shaar, Frankel and Yifrach families," Maj. Gen. Nitzan Alon, with the Israel Defense Forces, told reporters.

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He vowed to pursue those responsible.

"The war on terror continues. It didn't begin now and it will not be over soon," Alon told reporters.

"We will do whatever it takes to deter Hamas and other terrorists and we'll continue to fight terror using every legal means at our disposal."

An aunt of one of the victims told CNN she was still in shock.

"I'm holding his picture and I see his smile," said Leehy Shaar, Gilad Shaar's aunt. "He's so young and innocent ... It's just too sad to even imagine."

'United in mourning'

Netanyahu called an emergency security Cabinet meeting about the issue Monday.

"All Israel tonight is united in mourning the three teens who were brutally murdered by the Hamas terrorists," said Mark Regev, a spokesman for the Prime Minister, stressing that Israel will "continue to act against Hamas in order to protect our people."

"Hamas says every Israeli man, woman and child, every civilian, is a legitimate target for these sort of terrorist attacks, so we're totally within our rights to protect ourselves against those Hamas terrorists who want to kill our people," Regev said.

When asked whether he holds the Palestinian Authority responsible in any way for the teens' deaths, he responded: "It's clear that the terrorists came from areas under Palestinian Authority control and returned to territories under Palestinian Authority control."

The spokesman urged Palestinian Authority President Mahmoud Abbas to annul his pact with Hamas.

His comments were echoed by U.S. Reps. Ileana Ros-Lehtinen, R-Florida, chairman of the House Middle East and North Africa subcommittee; and Ted Deutch, D-Florida, ranking member of that subcommittee.

"We will continue to support the government of Israel in its efforts to bring the perpetrators to justice, and we offer the people of Israel our deepest and most heartfelt condolences as we grieve with them. If it is determined that Hamas is behind this horrific tragedy, Abu Mazen must immediately break up the unity agreement between Fatah and Hamas, a U.S. designated foreign terrorist organization," they said in a statetment.

Abu Mazen is another name for Abbas, whose government now includes Hamas, which controls Gaza.

Global outcry

Abbas called an emergency meeting of his own. The Palestinian leadership is expected to meet Tuesday to discuss the developments.

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U.S. President Barack Obama, Pope Francis and U.N. Secretary-General Ban Ki-moon were among world leaders condemning the killings Monday.

"As a father, I cannot imagine the indescribable pain that the parents of these teenage boys are experiencing. The United States condemns in the strongest possible terms this senseless act of terror against innocent youth," Obama said in a statement.

He continued: "From the outset, I have offered our full support to Israel and the Palestinian Authority to find the perpetrators of this crime and bring them to justice, and I encourage Israel and the Palestinian Authority to continue working together in that effort. I also urge all parties to refrain from steps that could further destabilize the situation."

Last week, the Israel Security Agency said it believed that two "Hamas activists from Hebron" were behind the teens' disappearances. It identified them as Marwan Qawasmeh, 29, and Amar Abu-Isa, 32.

As Israeli media were reporting on the bodies' discovery Monday night, Israeli forces were blocking roads into Hebron, a city in the southern West Bank. Fighter jets could be heard flying low over Gaza.

Overnight into Tuesday, more than 40 Israeli airstrikes hit Gaza, according to Palestinian security and medical sources. The strikes targeted Hamas, Islamic Jihad and other militant groups, the sources said.

The Israeli military later said that forces had carried out strikes against 34 targets in Gaza, targeting terror infrastructure, after the firing of 18 rockets at Israel since Sunday evening.

Within days after the teens disappeared, Israeli security forces conducted an extensive search for them and detained more than 150 Palestinian suspects.

Netanyahu blamed Hamas for the kidnappings almost immediately. A Hamas spokesman said in the days after the abductions that the Prime Minister's comments attributing blame were "stupid and baseless."

Also in the days after the abductions, the mother of one of the teenagers spoke to reporters.

The three "were just on their way home," said Naftali's mother, Racheli Frankel. "We trust" that they "will be with us here, and we'll hug them soon."