Saddam said he had not eaten in three days, while his former intelligence chief, Ibrahim Barzan, said he had been on strike for two days.
Their claims of a hunger strike could not be independently confirmed. The defendants are being held in US detention, and American officials could not immediately be reached to comment.
Investigative judge Raid Juhi did not deny the defendants were refusing food when asked about the strike after the day's three-hour session.
Chief judge Raouf Abdel-Rahman, who took over the court last month, has worked to impose order in a court where outbursts and arguments have frequently overshadowed the testimonies given in court.
At the start of yesterday's session, Saddam told the judge: "For three days we have been holding a hunger strike protesting against your way of treating us against you and your masters."
Ibrahim, who wore only his long underwear for the second day in a row, complained that he and the other defendants had been forced to attend the proceedings against their will.
The defendants refused to attend sessions last month after their defence team walked out of court. The defence lawyers have refused to participate in the trial until Judge Abdel-Rahman is removed, accusing him of bias against Saddam.
Judge Abdel-Rahman appointed new defence lawyers, but Saddam and other defendants refused to accept them. But on Monday, Judge Abdel-Rahman ordered the defendants to attend the session. Saddam entered on his own, but Ibrahim had to be pulled into the court, shouting and struggling.
The prosecution continued its attempts to prove Saddam and his seven co-defendants were directly involved in a wave of arrests and executions that followed a 1982 attempt on his life in the Shi'ite village of Dujail.
It put three former members of Saddam's regime a former secretary of Saddam, a former governor and an anonymous intelligence official on the witness stand in three hours of testimony, before the judge adjourned the proceedings until February 28.
The prosecution displayed to the court a document dated July 21, 1982 12 days after the assassination attempt in which the Mukhabarat, the intelligence agency headed by Ibrahim, recommended rewards for six employees officials for their role in the arrests.
The document bore a signature that the prosecution said was Ibrahim's.
Below it was written the word "agreed" with what was allegedly Saddam's signature.