Three Israeli teenagers who were abducted earlier this month in the West Bank have been found dead.
An Israeli military spokesman said their bodies were found in a pit near the town of Halhul, north of Hebron.
Naftali Frenkel and Gilad Shaar, both aged 16, and 19-year-old Eyal Yifrach were last seen at a junction near Hebron as they hitchhiked home.
Prime Minister Benjamin Netanyahu said Hamas was responsible, a claim the Palestinian militant group has denied.
At the start of a meeting of the Israeli security cabinet, Mr Netanyahu said the three were "kidnapped and murdered in cold blood by animals" and promised: "Hamas will pay".
But Hamas spokesman Sami Abu Zuhri told the AFP news agency that any action to punish the movement would "open the gates of hell".
Analysis: Yolande Knell, BBC News, Jerusalem
This site where the teenagers' bodies were found is just 10 minutes' drive from where the young Israelis were last seen two-and-a-half weeks ago.
Halhul is a turnoff from Route 60 - a busy road connecting the southern West Bank with Jerusalem. I watched Israeli soldiers operate a roadblock at this junction in the first days of their search.
Israeli officials accuse the Palestinian Islamist movement Hamas of killing the young Israelis. There are now calls for the group to be "eradicated".
These deaths are a tragedy for the families of the Israeli students, but they could also have deep political implications.
Israel's Shin Bet security service earlier said the main suspects in the case were two men named Marwan Qawasmeh and Amer Abu Aisheh and that they were "Hamas operatives".
Forensic teams were in the area and searches were continuing in an effort to capture "all those involved in this attack", it added.
Israeli security forces have set up blockades and closed down whole areas around Halhul, which is just a few kilometres from where the teenagers were last seen.
Israeli Economy Minister Naftali Bennett wrote on Facebook: "Murderers of children and those who direct them cannot be forgiven. Now is a time for actions, not words."
Israeli President Shimon Peres said the "whole nation is in deep grief".
"Amid our deep sorrow, we remain determined to fiercely punish the criminal terrorists," he added.
Palestinian Authority President Mahmoud Abbas has called an emergency meeting of the Palestinian leadership to discuss the teenagers' deaths.
Hamas spokesman Sami Abu Zuhri wrote on Facebook : "The occupation bears responsibility for escalation. Netanyahu tries to turn the picture upside down and he must understand his threats do not terrify us."
US President Barack Obama White House has condemned the "senseless act of terror against innocent youth," and urged "all parties to refrain from steps that could further destabilize the situation".
One of the teenagers, Naftali Frenkel, held dual Israeli-American citizenship.
A spokesman for Pope Francis, in the Vatican, condemned the killing of the teenagers as a "hideous and unacceptable crime" and "a grave obstacle on the path towards peace," Reuters reports.
Meanwhile, UN Secretary General Ban Ki-moon has called on both sides to "refrain from any actions that could further escalate this highly tense situation".
The abduction of the three Jewish seminary students on 12 June sparked a huge search operation in Palestinian towns and cities across the West Bank.
More than 400 Palestinians have been arrested, while five have been killed in fighting with Israeli troops.
Earlier, there were reports of clashes between Israeli soldiers and Palestinians in the Halhul area.
The case has put serious strain on relations between Israel and the Palestinians.
Mr Netanyahu has said the incident is a consequence of "the partnership" between Hamas and the Fatah movement of Palestinian Authority President Mahmoud Abbas. The two signed a reconciliation deal in April after years of division and formed a unity government earlier this month.