The disgraced former Israeli President, Moshe Katsav, has arrived at Maasiyahu prison near Tel Aviv to begin a seven-year sentence for rape.
Leaving his home in the town of Kiryat Malachi, he insisted he was innocent and accused the state of "executing" him and "burying a man alive".
Katsav's case has entranced and horrified the Israeli nation.
He was convicted a year ago, but was allowed to remain free while he appealed against the conviction.
Katsav, who turned 66 on Monday, resigned from the largely ceremonial post of president two weeks before his seven-year term was to expire in 2007, under a plea bargain that would have allowed him to escape a prison sentence.
But he then rejected the deal he had struck with prosecutors, vowing to prove his innocence in court.
In November, the Supreme Court unanimously upheld his conviction for raping a former employee when he was a cabinet minister in the 1990s, and for sexually harassing two other women while president.
"Moshe Katsav will go to jail as planned and will receive the same conditions as other prisoners," Israel's minister for internal security, Yitzhak Aharonovich, told Israel Radio on Tuesday.
Katsav will be placed in a wing at Maasiyahu that is reserved for observant Jews, and will share a cell with ex-government minister Shlomo Benizri in a move intended to ease his transition, reports say.
He will be assigned a special warden to ensure he does not attempt suicide, Prisons Service chief Aharon Franco told a Knesset hearing on Tuesday, according to the Jerusalem Post. Katsav's lawyers have expressed concerns about his state of mind.
Inmates in the religious section at Maasiyahu rise at 04:30, attend morning prayers and spend much of their time in religious study, with no access to television.
After serving a quarter of his sentence, Katsav could become eligible for spells of leave away from prison and could even apply to have his term reduced, the Associated Press news agency quoted Prisons Service spokeswoman Sivan Weizman as saying.
But he would have to admit guilt and express remorse, she said - something he has so far refused to do.
Katsav looked agitated and overwhelmed as he left his house on Wednesday morning.
"The State of Israel is executing a man today on the basis of impressions, without real time testimony, without evidence," he told reporters. "One day, consciences will prick and you will see that you buried a man alive."
Katsav is the first former Israeli head of state to be jailed.
The BBC's Wyre Davies in Jerusalem says the case has embarrassed many in Israel, where some commentators say Katsav should never have been elected president when there were so many rumours circulating about his conduct.
But others say the jailing of such a high-profile figure is proof that Israel has a strong legal system and, uniquely in the Middle East, is a country where sexual assault against women is taken seriously.