— Prime Minister Benjamin Netanyahu said Sunday that three Israeli teenagers who went missing in the West Bank on Thursday night were kidnapped by “members of Hamas,” the Islamist militant movement that controls the Gaza Strip and is a partner in the new Palestinian unity government.

Netanyahu’s claim of Hamas involvement came after Israeli security forces detained 80 Palestinians early Sunday in a sweep that stretched across the West Bank.

Among those arrested were top Hamas political leaders, former government ministers and members of Hamas’s militant wing. University lecturers, clerics and members of the group Islamic Jihad also were detained.

Israel vowed that it would not only punish the kidnappers and Hamas, but also hold the Palestinian Authority (PA) and its president, Mahmoud Abbas, responsible for the abductions.

“We will respond with an iron fist to terror,” said Naftali Bennett, Israel’s economics minister and the third most powerful member of Netanyahu’s coalition government.

The three teenagers, ages 16 to 19, attended religious schools in the West Bank and were abducted Thursday evening as they hitchhiked home. One of the youths managed to make a cellphone call to a police emergency line and say, “We’ve been kidnapped.”

Relations between Israel and the Palestinian Authority were already at a low point, after the collapse of U.S.-brokered peace talks in April and the creation this month of the unity government backed by Hamas and Abbas’s Fatah movement. Israel and most of the West consider Hamas a terrorist organization.

The kidnappings have riveted Israeli society and dominated the news cycle here. Tens of thousands gathered at Jerusalem’s Western Wall to pray for the teens’ safe return. Israel has thrown an entire paratrooper brigade into the search, and the West Bank city of Hebron — near where the teens were last seen — has been cordoned with checkpoints as Israeli security forces carry out house searches.

“Our government will extract a heavy price from the Palestinian leadership,” Deputy Defense Minister Danny Danon said Sunday. “We are not ruling out any options when it comes to possible actions against the PA government in both Gaza and Ramallah.”

Palestinian officials said they have been put in an impossible position. Ehab Bessaiso, a spokesman for the unity government, said the Palestinian Authority cannot be held responsible for abductions in Area C of the West Bank, on the outskirts of Hebron, near the Jewish settlement communities of Gush Etzion, where the Israeli military has complete security control and where Palestinian police are forbidden.

Netanyahu was dismissive of such assertions.

“When an attack takes place in Tel Aviv or in London or in New York . . . the question is not where the attack takes place, the question is where it originated,” Netanyahu said. “The kidnappers in this case set out from territory controlled by the Palestinian Authority, and the PA cannot absolve itself of its responsibility.”

Israeli soldiers use a drone during a military operation to search for three missing Israeli teenagers near the West Bank city of Hebron on June 14. (Abir Sultan/European Pressphoto Agency)

But a senior Israeli military intelligence officer, who gave a briefing to foreign reporters on the condition of anonymity, said security forces under the Palestinian Authority have been working closely with their Israeli counterparts — even now — to foil attacks against Israelis.

The officer would not divulge whether the Israelis believe that the “members of Hamas” thought to be behind the abduction were part of a relatively independent local cell or were getting instructions and support from commanders in the Hamas military wing.

The officer did say that independent local cells have previously carried out shootings and grenade attacks, while Hamas operatives answering to an “institutional” command structure have handled more complex actions such as suicide bombings and kidnappings.

Netanyahu said the abductions are proof that the reconciliation government that ended the seven-year feud between Hamas and Fatah poses a direct threat to Israeli civilians.

“You remember that Israel warned the international community about the dangers of endorsing the Fatah-Hamas unity pact,” Netanyahu said.

Diplomats from the United States and the European Union have said they will work with the unity government because no Hamas members serve as ministers.

Secretary of State John F. Kerry on Sunday appeared ready to blame Hamas for the abductions. “We are still seeking details on the parties responsible for this despicable terrorist act, although many indications point to Hamas involvement,” Kerry said. “As we gather this information, we reiterate our position that Hamas is a terrorist organization known for its attacks on innocent civilians and which has used kidnapping in the past.”

Hamas spokesman Sami Abu Zuhri called the accusations against the Islamist movement “stupid” and said they were “designed to break Hamas” and reflect a “state of confusion” among Israeli security forces.

Barak Ben-Zur, a former head of research for Israel’s Shin Bet security agency, said, “The Israeli security establishment is convinced that Hamas is behind the kidnapping,” even if it was the work of a local cell.

Ben-Zur said the rocky hills and deep valleys around Hebron favor the kidnappers. “It is very easy to hide in those places, very easy to disappear,” he said.

Anne Gearan in Washington and Ruth Eglash in Jerusalem contributed to this report.