Israel has vowed to make Hamas pay for the murder of three kidnapped Israeli teenagers, but the Islamist movement warned any reprisal attacks would open "the gates of hell".

Israeli prime minister Benjamin Netanyahu announced on Monday evening the discovery of the three bodies in a field in the southern West Bank.

"This evening, we found three bodies and all the signs indicate that they are the bodies of our three kidnapped youngsters," Netanyahu told ministers at the start of an emergency session of his security cabinet.

"They were kidnapped and murdered in cold blood by human animals," he said. "Hamas is responsible and Hamas will pay."

Hamas, which had denied any involvement in the abduction of the teenage boys, issued a warning in return to the Israelis.

"If the occupiers carry out an escalation or a war, they will open the gates of hell on themselves," Hamas spokesman Sami Abu Zuhri told AFP.

The discovery of the boys' bodies - one 19-year-old and two aged 16 - came 17 days after they disappeared, triggering a huge manhunt during which five Palestinians were killed and more than 400 arrested.

Two Hebron Hamas men named by Israel as prime suspects – Marwan Qawasmeh and Amer Abu Eishe – remain at large but Palestinian witnesses said troops blew up their homes early on Tuesday.

The Israeli roundup – mainly of people linked to Hamas – brought a wave of rocket attacks into southern Israel by militants in the Gaza Strip, answered in turn by Israeli air strikes.

The latest round began in the early hours of Tuesday morning with a rocket landing in the Negev desert region. An army statement said nobody was hurt.

Shortly afterwards the Palestinian interior ministry reported around 30 Israeli air strikes on deserted militant training sites across Gaza but there were no immediate reports of casualties.

In the northern West Bank, Israeli troops shot dead a young Palestinian early Tuesday during a raid into the Jenin refugee camp, Palestinian security and medical officials said.

They named the dead youth as Yusuf Abu Zagher, 18, and said the incident appeared unrelated to Israeli operations in the southern part of the territory.

The Israeli military had no immediate comment.

The youngsters' bodies were found near the West Bank town of Halhul, some 10 minutes drive from the roadside where they were last seen hitchhiking.



"During the search for Eyal Ifrach, Gilad Shaer and Naftali Frankel, the IDF discovered three bodies," the Israeli army said on Twitter.

Army spokesman Lieutenant Colonel Peter Lerner refused to comment on the cause of death.

He told reporters the bodies were being transferred for formal forensic identification.

One of the civilian volunteers involved in the search told army radio the bodies had been found under a pile of branches and stones in a remote area.

"Today, during a sweep with the army, one of the guys spotted something unusual, they started to move branches and stones and found the bodies," said volunteer Benny Truper.

"It was a very isolated area, more or less at the end of the world."

US President Barack Obama on Monday condemned the killings and warned against actions that could further "destabilise" the situation, amid the threats of retaliation against Hamas.

"The United States condemns in the strongest possible terms this senseless act of terror against innocent youth," Obama said in a written statement.

President Mahmud Abbas convened an emergency meeting of the Palestinian leadership to discuss the latest developments.



Abbas has come under massive Israeli pressure to renounce a reconciliation agreement with Hamas under which a merged administration for the West Bank and Gaza was formed in early June for the first time in seven years.