Nearly 30,000 Israelis converged on the Western Wall plaza in the Old City of Jerusalem Sunday evening to pray for the safe return of three Israeli teenagers kidnapped Thursday night as they were hitchhiking home from their boarding schools.

Meanwhile, the Israel Defense Forces continued its intensive manhunt, arresting nearly all the members of the Hamas leadership in the West Bank in the early hours of Monday morning, including the speaker of the Palestinian parliament, hoping to unravel the mystery of where the three boys – Eyal Yifrach, 19, Gilad Shaar, 16, and Naftali Frenkel, 16, a dual U.S.-Israeli citizen – were taken.

Thousands of Jews gather for a mass prayer for the release of three Jewish teenagers, believed to have been snatched from an area between the West Bank towns of Bethlehem and Hebron while hitchhiking, at the Western Wall in Jerusalem's Old City on June 15, 2014. Israeli Prime Minister Benjamin Netanyahu accused the Islamist Hamas movement of kidnapping three teenagers on the third day of a massive West Bank manhunt for the missing youths. (Photo: Ahmad Gharabli/AFP/Getty Images)

Thousands of Jews gather at the Western Wall in Jerusalem’s Old City for a mass prayer for the release of three Jewish teenagers believed to have been snatched from an area between the West Bank towns of Bethlehem and Hebron while hitchhiking, June 15, 2014. (Ahmad Gharabli/AFP/Getty Images)

The mother of one of those kidnapped said she had a greater sense of optimism because of the combination of the intelligence search coupled with prayers for her son’s safety.

“We are optimistic, with God’s help, he will see the combined effort of the prayers and solidarity, and we will embrace Naftali, Eyal and Gilad here,” said Racheli Frenkel, mother of Naftali Frenkel.

The Jerusalem Post reported Monday that “nearly all Hamas leaders” in the West Bank had been taken into Israeli custody for questioning. Despite two unsubstantiated claims of responsibility by lesser-known terrorist groups, Israeli Prime Minister Benjamin Netanyahu said Sunday that Hamas was behind the kidnapping, an allegation that was bolstered by U.S. Secretary of State John Kerry.

“We are still seeking details on the parties responsible for this despicable terrorist act, although many indications point to Hamas’ involvement,” Kerry said in a statement Sunday. “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.”

Aziz Dweik, the Hamas speaker of the Palestinian Legislative Council who is second in line in power after Palestinian Authority President Mahmoud Abbas, was taken into Israeli custody from his Hebron home, Israeli and Palestinian media reported.

Other prominent local Hamas figures were arrested, the Jerusalem Post reported, among the estimated 150 Palestinians who have been taken into Israeli army custody since the Thursday kidnapping.

Hamas spokesman Sami Abu Zuhri on Sunday denied Hamas was behind the kidnappings and called Netanyahu’s accusation “stupid.”

Israeli soldiers patrol during a military operation to search for three missing teenagers outside the West Bank city of Hebron, Sunday, June 15, 2014. (Photo: AP /Majdi Mohammed)

Israeli soldiers patrol during a military operation to search for three missing teenagers outside the West Bank city of Hebron, Sunday, June 15, 2014. (AP/Majdi Mohammed)

On Monday, a full four days after the boys were kidnapped, Abbas issued his first public statement condemning both the abductions and Israel’s response to it. The “Palestinian presidency condemns … the kidnapping of three Israeli boys and the series of Israeli violations,” the statement said, according to Reuters.

Netanyahu’s office announced that Netanyahu and Abbas had spoken by telephone Monday, in which Netanyahu said, “I expect you to help in the return of the kidnapped youngsters and in catching the abductors.”

Senior Israeli defense officials hinted that the punishment against Hamas was likely to increase; IDF Chief of Staff Benny Gantz said, “We’re heading towards an extensive operation.”

“We will know how to exact a very heavy price from the leaders of Hamas wherever and whenever we find it appropriate,” Defense Minister Moshe Ya’alon said, according to the Times of Israel.

One Palestinian was killed overnight during clashes with IDF forces in the area of Ramallah, the independent Palestinian news agency Ma’an reported.

Uzi Landau, the Israeli tourism minister, appeared to lay some of the blame for the kidnapping with the Obama administration, which earlier this month announced that it would work with and fund the Hamas-backed Palestinian unity government, a move decried strongly by top Israeli officials and members of U.S. Congress from both sides of the aisle.

“Unfortunately, with the establishment of the Abbas-Hamas government, we warned of the harm the Israeli public may suffer, and unfortunately our predictions were confirmed,” Landau said in a statement Monday. “The willingness of the US administration to effectively recognize the Abbas-Hamas government causes damage to the security of Israel’s citizens and encourages terror.”

The brother of Eyal Yifrach, one of the boys who disappeared, led the worshipers in Jerusalem “with brokenhearted prayer, sobbing as he recited verse after verse from the Book of Psalms,” the Times of Israel reported.

Photo: Ahmad Gharabli/AFP/Getty Images

Ahmad Gharabli/AFP/Getty Images

“We are proving to our enemies that the people of Israel live on, and we will never be broken,” said Chief Rabbi David Lau, who attended the service. “The entire nation came to the Western Wall tonight, as one person with one heart, united in prayer for the safety of the hostages; may they soon return to their families and their nation.”

Lau has urged Pope Francis to use his influence to help secure the teenagers’ release.

At the high school where two of the boys study, their fellow students have been holding marathon prayer and study sessions.

“All we have left now is to turn to our Father in Heaven and plead. … What we can do, and this has been the Jewish way from time immemorial, is to add more holiness and learn more Torah,” said Rabbi Adin Even-Israel Steinsaltz, the founder of the Mekor Haim religious high school seminary.

Bat-Galim Shaar, mother of Gilad, said she felt blessed by so many praying for her son.

“We are sending all these positive energy to our Gilad. Gilad is strong, and I’m sure Naftali and Eyal are strong as well. I want to ask the people of Israel, Keep praying together! Continue to empower our children. With the help of God, with this unity, we will succeed,” she said.

Even as Israelis offered prayers, Palestinians of all ages from both Hamas and Fatah celebrated the teenagers’ abduction by handing out sweets.