The second case relates to an alleged deal for favorable coverage with Arnon Mozes, publisher of prominent Hebrew-language daily Yedioth Ahronoth.
Netanyahu was interrogated in his residence in Jerusalem, while his wife was questioned at the National Economic Crime Unit, Lahav 433.
Last week, two Netanyahu confidants were arrested on suspicion of promoting regulation worth hundreds of millions of dollars to the Bezeq telecom company.
This week, Prosecutor Yehudit Tirosh, from the Assets Authority of Israel, assured in relation to Case 4000 that Netanyahu is in the heart of "a very serious case about giving and receiving bribes".
The Associated Press, alongside other agency cameras, caught detectives arriving in two vehicles around 9 a.m., but there has been no official police statement on the ongoing investigation.
Netanyahu's wife Sara was also questioned at the same time as her husband, at a police station near Tel Aviv, her lawyer told Reuters.
In addition, Israeli army radio said Friday that "a former senior communications ministry official close to the prime minister was detained this morning for questioning in the Bezeq affair".
Closing ceremony of 2018 Winter Olympics
The skiers and snowboarders accounted for 15 of the 23 total medals for the U.S.at the 2018 Winter Olympic games . This is not the first time that Russian Federation got involved with Olympic Games sabotage.
The development comes ahead of the prime minister's visit to Washington where he is to meet with President Donald Trump and speak before the pro-Israel lobby AIPAC next week.
Netanyahu has repeatedly denied any wrongdoing and has dismissed the accusations as a witch hunt orchestrated by a hostile media.
It is believed that police presented Benjamin and Sara Netanyahu with pieces of evidence collected throughout the investigation and asked them to comment on them.
In exchange Netanyahu allegedly raised the possibility of passing legislation to limit the circulation of Israel Hayom, a free newspaper that is the main rival to Yediot.
Meanwhile, about 70 protesters gathered outside Netanyahu's residence, demanding his resignation.
The Israeli media said Bezeq Israel Telecom controlling shareholder Shaul Elovitch and former Netanyahu spokesman Nir Hefetz were also being questioned.
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. In the meantime, Netanyahu is not obligated to resign and has indicated he will fight the charges while remaining in office.