Israel has broadened the search for three teenagers believed kidnapped by militants, arresting 80 Palestinians overnight and imposing a tight closure on the southern West Bank city of Hebron.

It was the biggest arrest operation in years and came after Prime Minister Benjamin Netanyahu ordered security forces to “use all tools at their disposal” to find the three teenagers he said had been “kidnapped by a terror organisation.”

Most of those arrested belonged to the Islamist movement Hamas, and included several members of the Palestinian parliament, Israeli press reports said.

“In a combined … effort to return the three abducted Israeli teenagers, approximately 80 Palestinian suspects were detained in a widespread overnight operation,” an army statement said, with a spokesman warning troops would leave no stone unturned.

“Palestinian terrorists will not feel safe, will not be able to hide and will feel the heavy arm of the Israeli military capabilities,” Lieutenant Colonel Peter Lerner said.

As the massive manhunt for the missing teens entered its third day, the defence ministry imposed a complete lockdown on the southern city of Hebron and the surrounding area, as well as a closure on the Gaza Strip.

The closure on the Hebron district began at midnight, a defence ministry statement said indicating that access to Gaza via the Erez crossing would be limited to humanitarian cases only, while only fuel would be allowed in through the southern goods crossing.

Inside Hebron, the West Bank’s largest city, Israeli paratroopers fanned out across the streets, and no cars were allowed in or out of the city, an AFP correspondent said.

Palestinian vehicles are stopped at an Israeli road block. Photo: Getty.

After late-night consultations with his security cabinet, which ended close to midnight, Netanyahu was to convene the weekly cabinet at his office at the defence ministry in Tel Aviv, his office said.

Overnight, hundreds of people gathered at the Western Wall in Jerusalem’s Old City to pray for the safe return of the teenagers.

“Our young people have been kidnapped by a terror organisation … there is no doubt about that,” Netanyahu told reporters in Tel Aviv late on Saturday.

The youngsters, one of whom also holds a US passport, are believed to have been snatched Thursday night from the Gush Etzion settlement bloc between Bethlehem and Hebron, reportedly while hitchhiking.

The missing teenagers, who study at two Jewish seminaries in the West Bank, have been identified as Gilad Shaer, 16, from Talmon settlement near Ramallah, Naftali Frenkel, 16, from Nof Ayalon in Israel, and Eyal Ifrach, 19, from Elad near Tel Aviv.

Netanyahu said he placed responsibility for their safe return on the shoulders of Palestinian president Mahmud Abbas and his Palestinian Authority, saying they must do “whatever necessary to help the hostages get home safely”.

The suspected abductions occurred 10 days after a new Palestinian unity government was sworn in, pieced together with the Islamist Hamas movement.

Israel has vowed to boycott all contact with the new government, whose emergence has ended seven years of divided rule between the West Bank and Gaza, with Netanyahu insisting Abbas be held responsible for all acts of violence emanating from anywhere in the Palestinian territories.

Israeli and Palestinian officials confirmed Palestinian security services were assisting in the search for the youths, who are believed to be “still alive”, Defence Minister Moshe Yaalon said on Saturday.

– Hazem Bader