Israeli police were expected to question Prime Minister Benjamin Netanyahu Monday over whether he illegally accepted gifts from wealthy supporters, media reports said, in a probe shaking the country's political scene.
The long-running inquiry has looked into whether Israeli and foreign businessmen have offered gifts worth tens of thousands of dollars as well as another unspecified issue, according to the reports.
Attorney general Avichai Mandelblit has reportedly decided to upgrade the inquiry to a criminal probe, though he has yet to confirm this.
Police and Netanyahu's office declined to comment on Monday.
Public radio said Netanyahu has agreed to be questioned at his residence. It was not clear when it would occur, though some reports said it would not be until 7:00 pm (1700 GMT).
Screens were mounted at the entrance to the compound in central Jerusalem in an apparent bid to shield the investigators' arrival.
In a Facebook post at the weekend, Netanyahu rejected all allegations against him and said his political opponents and some news outlets wanted to bring down his government.
Police have carried out the inquiry in secret over the course of some eight months and recently arrived at an important breakthrough, reports said. Some 50 witnesses are said to have been questioned.
In July, Mandelblit said he had ordered a preliminary examination into an unspecified affair involving Netanyahu, with no details given.
US billionaire and World Jewish Congress president Ronald Lauder has been among those questioned in the probe over gifts he allegedly gave Netanyahu and alleged spending on trips for him, Israeli media reported.
Lauder, whose family founded the Estee Lauder cosmetics giant, has long been seen as an ally of Netanyahu, who in the late 1990s put him in charge of negotiating with then Syrian president Hafez al-Assad.
- 'Campaign of provocation' -
Netanyahu has acknowledged receiving money from French tycoon Arnaud Mimran, who was sentenced to eight years in prison over a scam amounting to 283 million euros involving the trade of carbon emissions permits and the taxes on them.
Netanyahu's office said he had received $40,000 in contributions from Mimran in 2001, when he was not in office, as part of a fund for public activities, including appearances abroad to promote Israel.
He has also come under scrutiny over an alleged conflict of interest in the purchase of submarines from a German firm.
Media reports have alleged a conflict of interest over the role played by the Netanyahu family lawyer, David Shimron, who also acts for the Israeli agent of Germany's ThyssenKrupp, which builds the Dolphin submarines.
Beyond those issues, Israel's state comptroller released a critical report in May about Netanyahu's foreign trips, some with his wife and children, between 2003 and 2005 when he was finance minister.
Netanyahu, 67, is in his fourth term as prime minister and currently heads what is seen as the most right-wing government in Israeli history.
He has served as premier for a total of nearly 11 years, fast approaching revered founding father David Ben-Gurion's 13 years.
Polls have shown that if elections were held today, his Likud party would finish behind the centrist Yesh Atid, but that voters still prefer Netanyahu as prime minister.
The inquiry has led to fierce debate in Israeli politics, with Netanyahu's allies accusing opposition politicians and some in the news media of unfairly pressuring the attorney general.
Regional Cooperation Minister Tzachi Hanegbi, in comments on army radio on Monday, denounced what he called a "campaign of provocation and incitement" against Mandelblit.
Others have however accused Mandelblit of moving too slowly.
Netanyahu's predecessor as prime minister, Ehud Olmert, was forced to resign while dogged by corruption allegations.
He entered prison in February and is serving 27 months for corruption, making Olmert the first former Israeli premier to serve jail time.