In the newest investigation, known as Case 4000, police say the owners of an Israeli telecom giant Bezeq Israel Telecom provided favourable coverage of Prime Minister Benjamin Netanyahu in return for favours from communications regulators.
Israeli police questioned Prime Minister Benjamin Netanyahu on Friday for the first time in a corruption case that involves the country's largest telecommunications company Bezeq, Israel Radio said.
Along with two other corruption cases in which Netanyahu is suspected of bribery, the probes pose a serious threat to the four-term prime minister's political survival.
Netanyahu denies any wrongdoing in all the cases.
In the newest investigation, known as Case 4000, police allege that the owners of Bezeq Israel Telecom provided favourable coverage of Netanyahu and his wife on a news website they controlled, in return for favours from communications regulators.
A police spokesman declined to comment.
A Reuters cameraman saw a vehicle carrying two police officers pull into the prime minister's official residence on Friday morning.
Israel Radio said Netanyahu's wife Sara was providing testimony at the same time, at a police station near Tel Aviv.
The controlling shareholder of Bezeq Telecom, Shaul Elovitch, is currently in police custody, along with a former Netanyahu spokesman. They deny any wrongdoing.
A "witch hunt"?
Shlomo Filber, a confidant of Netanyahu and former director general of the Communications Ministry, has also been arrested in connection with the case, and has agreed to be a state witness, according to Israeli media.
Netanyahu, Israel's dominant political figure for a generation — in power since 2009, and for 12 years in total since 1996 — calls the allegations a "witch hunt" against him.
He has said that he will seek a fifth term in national elections next year.
Police recommended in February that Netanyahu be indicted in two other corruption investigations.
The attorney general must determine whether to accept police recommendations to charge him. The final decision in both cases could take months.
In one, known as Case 1000, he is suspected of bribery in receiving gifts from wealthy businessmen, which police say were worth nearly $300,000.
The other, Case 2000, involves an alleged plot to win positive coverage in Israel's biggest newspaper by offering to take measures to curtail the circulation of a rival daily.
So far, partners in Netanyahu's governing coalition have stood by him, saying they are awaiting the attorney general's next moves.
Political analysts say that could change if the investigations against Netanyahu intensify.
Netanyahu could also call a snap election to try to stall legal proceedings during the campaign and rally his right-wing power base behind him.