Israel said Hamas militants had abducted three Israeli teenagers in the occupied West Bank, warning of "serious consequences" as it pressed on with a search and detained dozens of Palestinians.
The two 16-year-olds and a third man aged 19 disappeared on Thursday night in the West Bank, where they were seminary students in a Jewish settlement.
"Those who carried out the kidnapping of our youngsters are Hamas people," Prime Minister Benjamin Netanyahu told his cabinet, referring to the Palestinian Islamist group that rules the Gaza Strip.
There has been no public claim of responsibility. Asked about Netanyahu's remarks, Sami Abu Zuhri, a Hamas spokesman in the Gaza Strip, stopped short of a clear denial or confirmation that it was involved.
Since the three went missing, the Israeli army has carried out house-to-house searches, round-ups and interrogations in the Palestinian city of Hebron and outlying villages.
In a statement, the military said "approximately 80 Palestinian suspects were detained in a widespread … operation".
Palestinian officials put the number of people taken into custody so far by Israeli authorities at more than 100 and said they included at least seven Hamas members of the Palestinian parliament and several prisoners recently released by Israel.
The incident tests ties between the Israeli government and Palestinian president Mahmoud Abbas.
"This will have serious consequences," Netanyahu said of the abductions.
Israel identified one of the students as Naftali Frankel, who also holds US citizenship.
Palestinian militants have said they want to kidnap Israelis to win concessions from the Israeli government, and the current incident coincides with a hunger strike by some 300 Palestinian prisoners protesting against detention without trial.
More than 1,000 Palestinian prisoners were freed in 2011 in exchange for the release of Gilad Shalit, an Israeli soldier held captive in the Gaza Strip for more than five years.