The IDF has arrested 80 Hamas members - including members of the Palestinian Legislative Council - in a massive wave of raids throughout the West Bank early on Sunday, as part of Israel's response to the kidnapping of three Israeli youths on Thursday.
While suspicions appear to be falling on Hamas as being behind the abduction,a security source said the wave of arrests did not mean that Hamas definitely carried it out.
He described the operational pattern of the kidnappers as "certainly being complex and different," suggesting that a terrorist organization was involved.
Hamas leaders Hassan Yousef, Wasfi Qabaha, Khaled Abu Arafeh and Mohammed Totah were among those arrested by the IDF, according to Palestinian reports.
The military also declared a closure for parts of the south Judea region, from Bethlehem southwards.
"The aim of this activity is to tighten the circle of intelligence," a senior army source said. He added that levels of violence in the West Bank remained under control, with one pipe bomb attack reported in Kalandia, and sporadic rock throwing.
Large numbers of infantry soldiers, including the Paratroopers' 35th Division, Kfir's 900th Division, and many intelligence units are on the ground, continuing to expand the operation.
On Saturday, security forces made "some progress" in efforts to track down the location of the abducted youths, the source said.
The IDF and Shin Bet [Israel Security Agency] made a number of arrests of Palestinians overnight in Judea, the source stated, as part of an effort "to get closer to the inner circle [of the terrorist cell] that handled the teenagers who disappeared."
"We are checking a number of directions," he continued, and warned that the search could span days, rather than hours. "All of our operational and intelligence systems have been very much involved in the past 24 hours, to try and retrieve the teenagers," he said.
On Saturday, the IDF deployed all of the battalions of the the 35th Paratrooper Brigade to the West Bank, as well as a number of special forces.
Khaled Abu Toameh contributed to this report.