Israeli police investigators interrogated on Monday Prime Minister Benjamin Netanyahu over corruption suspicions, Attorney General Avichai Mendelblit confirmed in a statement.
The interrogation ended at around 23:00 local time (2100 GMT), after at least three hours, a police spokesperson said.
It was the first time the General Attorney and the police officially acknowledged the investigation, which has been conducted for months with dozens of unconfirmed reports in the local media.
Attorney General Avichai Mendelblit said in a special statement that Netanyahu was interrogated over suspicions that he received "benefits" from businessmen.
He confirmed that the investigation was conducted under caution, meaning Netanyahu was investigated as a suspect.
The investigation involves "a slew of allegations that the prime minister allegedly committed offenses in the field of integrity," Mendelblit said, without elaborating.
The initial investigation led to several other affairs, Mendelblit said. The probe has been conducted for several months but in December the investigators found evidence that "changed the evidential situation of the case," leading to Monday's questioning under caution of Netanyahu.
Earlier on Monday, black screens were placed outside the prime minister's official residence in Jerusalem to block the view of journalists seeking to photograph the police investigators.
Netanyahu's office rejected the suspicions against him as "baseless." In a meeting of ministers from his Likud party, he said "They won't come to anything because there isn't anything."
Israel's Channel 2 TV news said that Netanyahu is under criminal investigation over suspicion that he and members of his family received "favors," including gifts and money, from Israeli and foreigner businessmen.
Media said the police are investigating a second graft affair under complete secrecy.
Israel's Ha'aretz newspaper reported that Ron Lauder, an American billionaire, was linked to the case. Lauder was Netanyahu's close friend until their relations reportedly soured.
According to the Ha'aretz, Lauder was investigated by the police when he arrived in Israel for the funeral of the late president, Shimon Peres, in September.
During his questioning, Lauder confirmed that he had given Netanyahu "various gifts, including a suit, and that he had also financed a trip abroad for the prime minister's son, Yair," Ha'aretz reported.
