JERUSALEM >> Israel’s prime minister on Sunday accused the Hamas militant group of kidnapping three Israeli teenagers who disappeared over the weekend, as the military arrested dozens of Palestinians and closed off West Bank roads in a frantic search for the youths.

The crisis escalated already heightened tensions between Israel and the new Palestinian government, which is headed by Western-backed President Mahmoud Abbas but backed by Hamas. Israel, which considers Hamas a terrorist group, has condemned the alliance and said it holds Abbas responsible for the teens’ safety.

"Hamas terrorists carried out Thursday’s kidnapping of three Israeli teenagers. We know that for a fact," Prime Minister Benjamin Netanyahu said. "Hamas denials do not change this fact."

Speaking in English, Netanyahu also tried to rally international opinion against the new Palestinian government. His calls for the international community to shun the government have been ignored so far.

"Instead of abiding by his international obligation to disarm Hamas, President Abbas has chosen to make Hamas his partner," he added. "I believe that the dangers of that pact now should be abundantly clear to all."

Netanyahu provided no evidence to back his claims. Palestinian officials rejected Netanyahu’s contention that they are responsible. Hamas, meanwhile, praised the apparent kidnapping but stopped short of accepting responsibility.

The three youths, Eyal Yifrah, 19, Gilad Shaar, 16, and Naftali Frenkel, disappeared Thursday night as they were heading home from a West Bank religious school.

Officials confirmed that one of the teens called a police emergency line around 10:25 p.m. and said, "We’ve been kidnapped." They have not been heard from since then.

Frenkel also holds American citizenship. Addressing reporters outside the family home in the central Israeli town of Nof Ayalon, his mother, Rachelle, thanked the public, the Israeli security services and the U.S. Embassy for offering support.

"The professional people will do their job, and we do trust them. And everybody else, if you could please pray with us," she said in English. "We trust that Eyal, and Gilad and Naftali, boys coming home on their way from school, they were just on their way home, will be here with us and we’ll hug them soon."

The case has riveted the nation’s attention, receiving around-the-clock coverage in local media. Late Sunday, more than 10,000 people converged at Jerusalem’s Western Wall, the holiest site where Jews can pray, for a special mass prayer, police said.

Palestinian militants have repeatedly threatened to kidnap Israelis, hoping to use them as bargaining chips to win the release of prisoners held by Israel. This would be the first time three civilians have been taken at the same time.

Military officials said that given the nature of the kidnapping, evidence pointed to Hamas involvement. A senior Israeli military intelligence officer said only the "most institutionalized cells … promote suicide bombers attacks and kidnapping." Asked whether this could refer to other groups beside Hamas, Lt. Col Peter Lerner said: "No."

U.S. Secretary of State John Kerry condemned the kidnapping but was more cautious about assigning blame.

"We are still seeking details on the parties responsible for this despicable terrorist act, although many indications point to Hamas’ involvement," he said.

The overnight arrest raid was concentrated in the southern West Bank city of Hebron, in the area where the youths disappeared. Israel imposed a closure on the area, restricting traffic in hopes of preventing them from being smuggled out.

A Hamas website said more than 60 of those arrested were members, including senior figures in the movement.

The Palestinians’ self-rule government, which administers 38 percent of the West Bank, has insisted it is not to blame, saying the teens went missing in territory under full Israeli control.

"The Israeli government cannot blame the Palestinians for security issues in areas that are not controlled by them," said Ehab Bseiso, the spokesman of the Palestinian unity government.

But Netanyahu rejected the claim as "absurd," saying the attackers had originated in Palestinian territory.

In its first statement on the issue, Hamas praised the kidnapping but did not claim responsibility. In a message sent to journalists, it referred to "the success of the kidnapping" and said that "the movement pays tribute to the heroes who are behind the kidnapping."

In the Gaza Strip, senior Hamas official Sami Abu Zuhri dismissed Netanyahu’s claims of Hamas involvement in the abductions as "silly."

Hamas governed Gaza for seven years before striking the unity deal with Abbas. Although it does not sit in the government, it has given its support and it remains the de facto power in Gaza.

Despite the exchange of accusations, security officials from Israel and Abbas’ forces have been cooperating closely in the West Bank trying to find the kidnappers.

Abbas met with his security chiefs late Saturday and urged them to do anything they can to contribute to the search, said a senior Palestinian official who spoke on condition of anonymity because he was not allowed to brief journalists.

In Egypt, a senior security official said Egyptian National Security was working through a third Palestinian party to help resolve the crisis. Egyptian authorities are in contact with Palestinian militant groups through intermediaries, since the Egyptian government does not maintain direct contact with Hamas. The official said the three Israelis were still believed to be in the West Bank.

Hamas, branded a terrorist group by the West for its long history of attacks on Israeli civilians, has been involved in past abductions.

But this time around, there are other potential suspects. In recent months, there have been growing signs of the emergence in the West Bank of small groups of militants who identify with al-Qaida.

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Yousur Alhlou in Jerusalem and Laura Dean in Cairo contributed to this report.