In a statement, the internal security agency confirmed its agents briefly detained and questioned Iranian-born Reza Aslan at a border crossing, saying his "behavior there raised suspicion."
It denied Aslan's claim he was questioned about his politics.
Aslan, 46, took to Twitter on Tuesday to describe his experience which happened two weeks ago when he arrived in Israel with his wife, children and in-laws after a visit to Jordan. He said he was separated from his family upon arrival at the border and detained by the Shin Bet, who allegedly warned him: "We can make it so you don’t see your kids for a long time."
The Shin Bet interrogator also allegedly told him: “You think because you’re a public person I can’t do whatever I want with you?”
"I was floored. This is how interrogations begin in police states," Aslan noted.
He then described the following exchange:
Shin Bet interrogator: "Why do you hate Israel?"
Aslan: "I don’t hate Israel."
Interrogator: "But you hate our Prime Minister."
Aslan: "I’m sorry is your Prime Minister Israel?"
Interrogator: "He was democratically elected!"
Aslan: "So was Trump and I hate him and still love America."
Interrogator: "Oh I know all about you and Trump."
"You don’t think Israel should exist yes?" the Shin Bet interrogator then allegedly asked him.
"That’s absurd. I’m against the occupation not Israel," he responded.
Then, he said, "the police state part began in earnest: Write down names of journalists you associate with. Write down names of Palestinian organizations you support. And constantly, repeatedly, this threat: 'if you don’t cooperate it will be a long time before you see your kids again.'"
Aslan said he tried to cooperate as best as he could, but was accused of lying over every answer he gave.
Aslan said the interrogation lasted for hours, at the end of which the Shin Bet interrogator agreed to let him into Israel but warned him "I may let you into Israel but, who knows, I may not let you out. I will keep you here and kick out your family. It depends on you. You would miss your kids yes?”
She also warned him not to enter the Palestinian territories, not to meet with or speak to any Palestinians or any Israeli troublemakers, and concluded with: "We are watching you."
Aslan concluded his tweets with harsh criticism against Israel, "This was my 4th trip to Israel in ten years and every time it’s gotten worse. It’s becoming unrecognizable as a democracy. It is becoming a full-blown police state."
"And it can’t last. When I was released my evangelical in-laws were in shock. 'I had no idea it was like this,' they said. Now they do. So do more Americans each day. And if Israel loses them, who will continue to shield it from pressure to change course? The clock is ticking," he cautioned.
This is the second such case that emerged this week. On Monday, American-Jewish journalist Peter Beinart, a vocal critic of Israeli policies, said he was also detained by the Shin Bet at Ben-Gurion Airport.
Beinart, who arrived in Israel for a family visit, was detained for an hour upon landing. He said he was sent to a small room where a security official asked about his political activities and whether he was involved in groups that advocate violence, threaten democracy or promote anarchy.
Beinart said he was then asked about his participation in a nonviolent West Bank protest two years ago.