JERUSALEM, June 17 (Xinhua) -- Israel's Shin Bet security agency said Sunday it arrested an "extraordinarily large terror cell" in the West Bank that planned bomb attacks in Tel Aviv and Jerusalem.

Some 20 members of the cell, based in the Nablus area, were caught and detained in April, but the arrests were kept under a court-ordered gag order.

The Shin Bet said in a statement released on Sunday that the investigation revealed that the cell members intended to carry out a bomb attack in Tel Aviv, a suicide attack in Jerusalem, a bomb attack in the settlement of Itamar, as well as shooting attacks in the northern West Bank.

"These attacks were thwarted, some at the last minute, due to the arrest of the infrastructure members," the statement read.

The Shin Bet said that during the investigation, several improvised explosive devices were seized, including one weighing 10 kg to be operated by a cellular phone.

Also, weapons were seized, as well as instructions for the manufacture of bombs and explosive materials, the Shin Bet said.

According to the Shin Bet, most of the operatives are members of Hamas, a Palestinian Islamist movement that runs the Gaza Strip.

An official, identified in the statement as "a senior Shin Bet officer," said this case shows the "desire and efforts that Hamas is investing in building terrorist infrastructures" in the West Bank.

Israeli Prime Minister Benjamin Netanyahu said in a statement that "Hamas is trying to attack us from both Gaza and Judea and Samaria (the Israeli name of the West Bank)," "This is why we will continue to maintain security control of all areas west of the Jordan River," said Netanyahu.

The arrests came amidst 2.5-month rallies near the Israel-Gaza fence to protest the crippling blockade Israel and Egypt have imposed on the enclave.

Israeli forces have used live fire against the protesters, killing at least 122 Gazans since the protest began on March 30.