JERUSALEM -- Israeli police were questioning Benjamin Netanyahu and his wife as part of an investigation into a corruption case involving the country's telecom giant on Friday, casting a shadow on the prime minister's upcoming visit to Washington. Television footage showed police investigators entering Netanyahu's residence. Reports said Netanyahu's wife, Sara, was being questioned at another location.

Last month, two Netanyahu confidants were arrested on suspicion of promoting regulation worth hundreds of millions of dollars to the Bezeq telecom company. In return, Bezeq's news site, Walla, allegedly provided positive Netanyahu coverage.

It's the first time that Netanyahu, who as prime minister also held the communications portfolio until last year, is being questioned over the affair, known as Case 4000.

The development comes ahead of Netanyahu's visit to Washington where he is to meet with President Donald Trump and speak before the pro-Israel lobby AIPAC next week.

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Police have recommended indicting Netanyahu on corruption charges in two other cases.

Netanyahu is accused of accepting nearly $300,000 in lavish gifts from Hollywood mogul Arnon Milchan and Australian billionaire James Packer. In return, police say Netanyahu operated on Milchan's behalf on U.S. visa matters, legislated a tax break and connected him with an Indian businessman.

In the other case, Netanyahu is accused of offering a newspaper publisher legislation that would weaken his paper's main rival in return for more favorable coverage. Netanyahu reportedly was recorded asking Arnon Mozes, the publisher of Yediot Ahronot, for positive coverage in exchange for helping to weaken Israel Hayom, a free pro-Netanyahu newspaper that had cut into Yediot's business.

Netanyahu has repeatedly denied any wrongdoing and has dismissed the accusations as a witch hunt orchestrated by a hostile media.

One of the two Netanyahu's confidants arrested last month has turned state witness and will reportedly incriminate him in the corruption allegations. Police would not confirm whether long-time aide Shlomo Filber would testify against Netanyahu, but all the major Israeli media outlets said a deal to do so had been reached.

Filber, the former director of the Communications Ministry under Netanyahu, was arrested on suspicion of promoting favorable regulation to Bezeq in return for Walla's alleged favorable coverage of Netanyahu and his family.