Israel's Prime Minister Benjamin Netanyahu has denied corruption charges during a brief court appearance, as his graft trial resumed weeks ahead of a fourth national election within two years. 

Mr Netanyahu, the first Israeli premier to be indicted in office, was formally charged last year over allegations of accepting improper gifts and seeking to trade regulatory favour with media moguls in exchange for positive coverage.

He had been compelled to appear in person to respond to the charges, after last month formally submitting his innocent plea in writing.

"I confirm the written answer submitted in my name," Israel's longest-serving premier said, after Jerusalem court judge Rivka Feldman Friedman asked his response to the charges against him.

Mr Netanyahu was referring to a 18 January court filing from his defence team which said "the prime minister denies all charges" in each of the three separate cases against him. 

The combative 71-year-old premier, who has previously blasted the charges as "fabricated and ludicrous", spent just 20 minutes at the hearing, entering and exiting amid a heavy security deployment and dozens of protesters. 

"I don't think they will rush" to start examining evidence before the March polls, Mr Netanyahu told journalists this evening.

"That would be seen as clear interference in the elections."

Mr Netanyahu has repeatedly claimed that he is the victim of a witch-hunt.

The hearing continued in his absence for several hours, with defence lawyers Boaz Ben Zur and Amit Hadad accusing Israel's Attorney General Avichai Mandelblit - an appointee of Mr Netanyahu - of mishandling the case.

They argued that elements of the investigation were opened without required authorisations.

The three-judge panel later released a ruling saying they would examine that complaint before moving forward with the prosecution's case. 

That could result in a delay that keeps Mr Netanyahu out of court until after the 23 March election. 

When Mr Netanyahu last appeared in court nine months ago, he had just won a political victory by forming a coalition government with election rival Benny Gantz, following three inconclusive national polls. 

But the fraught coalition proved short-lived and collapsed in December, with Mr Gantz branding Mr Netanyahu as serially dishonest.  

It is unclear whether the cloud of the trial will hurt the premier's re-election chances in March.

Israel's parliament speaker Yariv Levin, a Netanyahu loyalist from his right-wing Likud party, insisted the court must postpone the trial.

Proceeding now "will be lending a hand to blatant meddling in the elections", he told the right-wing Israel Hayom newspaper on Sunday. 

Several recent polls place the Likud comfortably in the lead, but it is far from certain that it will be able to form a 61-seat majority with its conservative and religious allies. 

4,000, 2,000, 1,000

The charges against Mr Netanyahu are divided into three separate cases. 

The most serious, in which the premier is accused of bribery, fraud and breach of trust, centres on the allegation that he negotiated with Shaul Elovitch of telecommunications giant Bezeq to secure positive coverage on his Walla! news site in exchange for policies benefiting Bezeq.

Mt Elovitch and his wife were also indicted in what is known as Case 4,000.

Case 2,000 concerns allegations Mr Netanyahu sought a deal with the owner of the Yediot Aharonot newspaper that would have seen it give him more favourable coverage.  

Case 1,000 involves allegations Mr Netanyahu and his family received gifts, including luxury cigars, champagne and jewellery estimated to be worth more than 700,000 shekels (€177,711) from wealthy individuals, in exchange for financial or personal favours.

He would be forced to resign if convicted with all appeals exhausted, but that process would likely take several years.

Weekly protests against him have rumbled on for months, with some demonstrators focusing on the graft allegations. 

Some protesters met Mr Netanyahu's motorcade outside the court carrying placards bearing the words "Crime Minister", while others taunted him as he entered and left the court. 

"We are here to swipe (away) all the dirt and all the corruption that he has created," protester Claudia Manoquian told AFP.