JERUSALEM, Jan. 2 (Xinhua) -- Israeli police investigators interrogated Prime Minister Benjamin Netanyahu over corruption suspicions, the Attorney General office confirmed on Monday night.

The interrogation ended at around 23:00 local time (2100 GMT), after at least four hours.

According to media reports, the investigation was conducted under caution, meaning Netanyahu was investigated as a suspect.

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.

In July, Attorney General Avichai Mendelblit said he had ordered a preliminary probe of an affair involving Netanyahu, but at that time he did not specify what the probe about.