Israel's Supreme Court on Thursday rejected an appeal lodged by former president Moshe Katsav, upholding his conviction on charges of rape and other sexual offences, press reports said.

The court also rejected an appeal against the seven-year sentence which he was handed in March.

Reading out their decision, the three justices unanimously ruled that the disgraced president was guilty of rape and rejected his "alternative scenarios," Israel's army radio reported.

Katsav, 65, was convicted in December 2010 of two counts of rape, sexual harassment, indecent acts and obstruction of justice after an 18-month trial which included harrowing accusations, and portrayed him as a sexual predator who routinely harassed his female staff.

In March, he was sentenced to seven years jail time, which he also appealed, but the judges rejected his appeal. He is likely to begin serving his sentence within the coming days, press reports said.

One by one, the judges refuted the claims made by the defence -- upholding his conviction for raping the main defendant, known only as "A" and rejecting his lawyers' claims that it was a consensual affair.

"We have unanimously decided to not change the District Court's decision on 'A' -- that he raped her," media reports quoted the judges as saying. "There is no evidence for the affair thesis."

They also rejected his appeal over a second count of rape against another woman as well as other charges of sexual harassment against two more women, ruling that their testimonies were reliable while the former president's was not.

In March, the court sentenced Katsav to seven years behind bars with a two-year suspended sentence and ordered him to pay compensation of $28,000 (20,000 euros) to the main victim, as well as $7,000 (5,000 euros) to a second victim.

Throughout the 18-month trial, which included harrowing accusations, the former president was portrayed as a sexual predator who routinely harassed his female staff.

But he denied the charges against him, saying he was the target of a media plot and that his interactions with his female staff were consensual.

The former president was scheduled to report to prison to begin serving his sentence on May 8, but the court agreed to delay the beginning of his sentence until he completed his appeal.