JERUSALEM, Jan. 5 (Xinhua) -- Israeli police said they interrogated Prime Minister Benjamin Netanyahu on Thursday night for suspicion of receiving "benefits," amidst a string of criminal investigations of corruption affairs.

The five-hour questioning took place at the prime minister's official residence in Jerusalem, where Netanyahu was questioned about two graft affairs on Monday.

The recent questioning was focused on a previously undisclosed case. "Today's interrogation also dealt with an additional affair," police spokeswoman, Luba Samri, said in a statement released after the questioning.

She declined to disclose any details on the case, citing fear of obstruction of investigation, but said that another person was interrogated for the same affair two days ago.

Samri said Netanyahu was interrogated under caution, meaning he was interviewed as a suspect.

Earlier on Thursday, Channel 2 TV news reported that officials involved in the investigation said that Arnon Milchan, a Hollywood producer and an ex-Israeli businessman, was involved in one of the cases.

According to the officials, Milchan spent "hundreds of thousands of shekels" to buy Netanyahu Cuban cigars. He also supplied "pink champagne" to Netanyahu's wife, Sara, Channel 2 said. The goods were sent to the Netanyahu as gifts over a period of at least seven years, the report said.

On Monday, Attorney General Avichai Mandelblit officially confirmed for the first time that Netanyahu was under criminal investigations. The statement followed months of unconfirmed reports in local media over the alleged prime minister's involvement in a series of corruption affairs.

Netanyahu dismissed the allegations as "baseless" and hinted it was part of a political prosecution aimed to remove him from the office. "There won't be anything because there isn't anything," he said earlier this week.