JERUSALEM -- Israel's attorney general on Thursday recommended indicting Prime Minister Benjamin Netanyahu with bribery, fraud and breach of trust in a series of corruption cases, a momentous move that shook up Israel's election campaign and could spell the end of the Israeli leader's illustrious political career.

Attorney General Avichai Mandelblit announced his decision after more than two years of intense investigations and deliberations.

Police had recommended indicting Netanyahu on various charges in three separate cases that ranged from accepting expensive gifts from wealthy allies to allegedly trading influence for more favourable press coverage.

The final decision on indictment will only take place after a hearing, where Netanyahu is given the opportunity to defend himself. That process is expected to take many months and be completed long after the April 9 elections.

But the recommendations immediately cast a cloud over the campaign and Netanyahu's future.

Appearing on national TV, Netanyahu dismissed the allegations as an "unprecedented witch hunt" by political opponents intent on ousting him. He called the timing, just weeks before the election, "outrageous" and appeared emotional at times as he dismissed the charges as a "blood libel." He vowed to debunk all allegations and said he would remain prime minister for "many years."

"Don't let this witch hunt affect you," he told Israeli voters.

An indictment would mark the first time in Israeli history that a sitting prime minister has been charged with a crime. Former Prime Minister Ehud Olmert served time in prison for corruption, but had already resigned by the time he was charged.

Netanyahu doesn't look to go that quietly. He denies any wrongdoing and calls the allegations a media-orchestrated campaign aimed at removing him from office. He has vowed to carry on and is deadlocked in the polls, 40 days before Israelis go to vote.

In a last-ditch effort to prevent the public release of an indictment, Netanyahu's Likud party petitioned the Supreme Court to have it delayed until after the elections. But the court rejected the request Thursday, clearing the way for the announcement from the attorney general.

Despite opposition calls for Netanyahu to step down, Likud and his other nationalist coalition partners have lined up behind him thus far, all but ruling out sitting in a government led by his primary opponent, retired military chief Benny Gantz.

While Israeli prime ministers are not required by law to resign if charged, the prospect of a prime minister standing trial while simultaneously running the country would be unchartered territory.

Mandelblit's decision could either galvanize Netanyahu's hard-line supporters who see him as a victim of an overzealous prosecution or turn more moderate backers against him who have tired of his lengthy rule tainted by long-standing accusations of corruption and hedonism.

Either way, the upcoming elections appear to be morphing into a referendum on Netanyahu as he seeks to become the longest serving premier in Israeli history. Netanyahu has been prime minister since 2009 and served a previous term between 1996 and 1999.

President Donald Trump, with whom Netanyahu has forged a close connection, offered the Israeli leader a boost ahead of the expected announcement.

"I just think he's been a great prime minister and I don't know about his difficulty but you tell me something people have been hearing about, but I don't know about that," he said in response to a question in Hanoi, where he was holding a summit with the leader of North Korea.

"I can say this: that he's done a great job as prime minister. He's tough, he's smart, he's strong," Trump said.

Netanyahu rushed back Wednesday from a diplomatic mission to Moscow, and a meeting with President Vladimir Putin, to prepare for his rebuttal to the charges.

The most serious allegations against Netanyahu involve his relationship with Shaul Elovitch, the controlling shareholder of Israel's telecom giant Bezeq.

Mandelblit recommended a bribery charge in the case based on evidence collected that confidants of Netanyahu promoted regulatory changes worth hundreds of millions of dollars to Bezeq.

In exchange, they believe Netanyahu used his connections with Elovitch to receive positive press coverage on Bezeq's popular subsidiary news site Walla. Police have said their investigation concluded that Netanyahu and Elovitch engaged in a "bribe-based relationship." A related charge against Netanyahu's wife, Sara, was dropped.

Mandelblit's statement said there was a unanimous opinion among investigators that the relationship between Netanyahu and the Elovitches constituted bribery.

"Everyone agreed there was enough evidence to prove that benefits were given to Netanyahu by Elovitch and his wife Iris Elovitch and were taken by Netanyahu in return for actions he took as part of his job," it said.

Mandelblit also filed breach of trust charges in two other cases. One involves accepting gifts from billionaire friends, and the second revolves around alleged offers of advantageous legislation for a major newspaper in return for favourable coverage.

Mandelblit's office said the timing of Netanyahu's hearing would be set in the near future in co-ordination with the prime minister's lawyers.