File photo: Nir Hefetz sits in the Magistrate Court next to a policeman during his remand hearing in Tel Aviv, Israel, February 22, 2018. (Reuters photo)

JERUSALEM, March 5 (Xinhua) -- Israeli Prime Minister Benjamin Netanyahu's former top adviser Nir Hefetz signed a state's witness agreement Monday in a high-profile corruption case involving the Israeli leader, officials said.

A police spokesperson said the deal with Nir Hefetz, a former media adviser for Netanyahu and his wife and the couple's close confidant, was signed on Sunday night.

Hefetz was released to a house arrest on Sunday after spending two weeks of detention in jail, during which he was investigated by the police's Lahav 433 special anti-corruption unit.

Israeli media reported that under the deal, Hefetz will give the police audio records involving at least three corruption affairs in which Netanyahu is a suspect. In return, Hefetz will receive full immunity: He will not stand to trial, spend time in jail, or be required to pay a fine.

The deal casts a long shadow on the visit of Netanyahu in Washington, where he is due to meet later Monday with U.S. President Donald Trump.

The move was widely described by local media as a dramatic development against the long-time Israeli prime minister.

Hefetz, considered to be one of his most loyal associates, was described also as Netanyahu's "spin doctor."

Hefetz is a suspect in two criminal cases. In the so-called "case 4000," he is suspected of being part of a bribery deal, in which Israel's largest telecom company, Bezeq, received regulatory and financial benefits from the Communication Ministry, which Netanyahu headed between 2014 and 2017, in addition to his capacity as prime minister.

In return, Walla, a news site controlled by Bezeq's control-holder, Shaul Elovitch, allegedly refrained from criticizing Netanyahu and gave him and his wife, Sara Netanyahu, positive coverage.

In the second case, dubbed by the police "case 1270," Hefetz allegedly tried to bribe Judge Hila Gerstal in 2015, who was a candidate for the position of the attorney general, offering her the office in exchange for dropping a case against Sara Netanyahu.

Hefetz, 52, served as Netanyhau's media adviser between 2014 and 2017. He kept close ties with the Netanyahus also after leaving the job.

He is the third associate who turns against Netanyahu, who denies any wrongdoing and charges he is a victim of a witch-hunt carried out by the media and "the left."

Netanyahu and his associates are suspected to be involved in at least five criminal corruption cases.

Last month, Israeli police recommended to indict Netanyahu for a series of serious corruption charges including bribery, fraud, and breach of trust in two other cases, "case 1000" and "case 2000."

In "case 1000," Netanyahu and his family allegedly received expensive cigars, champagne, and jewelry in a sum amounting to about one million shekels (about 282,800 dollars) from the Israeli businessman and Hollywood tycoon, Arnon Milchan, and Australian businessman, James Packer, between 2007 and 2016.

In "case 2000," Netanyahu allegedly received bribes from Arnon Mozes, the publisher of Yedioth Aharonoth, one of Israel's largest newspapers. According to the police, Netanyahu and Mozes held talks over an "exchange deal," in which Netanyahu would receive favorable coverage in Yediot Aharonot in return for promoting a law and other measures that would limit the distribution of Israel Hayom, Yedioth's main rival.

On Friday, Netanyahu and his wife were questioned for the first time in the "case 4000."

Netanyahu was questioned at the official Prime Minister's Residency in Jerusalem and Sara Netanyahu was questioned at the Lahav433 anti-corruption unit outside Tel Aviv.

The investigations sparked speculations that Netanyahu might call for early elections to reaffirm his public support. Opinion polls last Friday showed that his party, the Likud, maintains its power and would win the elections, despite the corruption suspicions.