Jerusalem (CNN) -- All of the Palestinians in Israeli prisons -- about 4,500 people -- took part in a hunger strike Sunday, and crowds protested in the streets of the West Bank as Palestinian officials called for an international investigation into an inmate's death.
A Palestinian official also sent a warning to U.S. President Barack Obama, who plans to make his first trip to Israel as president next month.
"If President Obama wants to visit the region peacefully, he should exert pressure on Israel to release the prisoners -- especially the ones who are on hunger strike -- or else he will visit while Palestine is on fire," Palestinian Minister of Prisoner Affairs Issa Qaraqe said.
Speaking at a news conference in Ramallah, Qaraqe demanded an international investigation.
Israel said doctors had worked to save the inmate, who was suffering from previous injuries. The prisoner, Arafat Jaradat, 30, died Saturday.
"The martyr Jaradat was subjected to extreme torture which led to his death, and there are no indications that he died from cardiac arrest as the Israeli occupation authorities claimed," Qaraqe said Sunday. He added that "signs of beating and torture appeared on his limbs, neck, and spine, and blood clots appeared around his mouth and nose."
He cited information from a Palestinian doctor who was present for the autopsy in Tel Aviv.
But the Israeli Health Ministry said the autopsy showed "no signs of external damage ... except the signs of cardiopulmonary resuscitation (CPR) and a small spot caused by an abrasion on the right breast."
There were blood clots in the muscle -- one on the shoulder and one on the side of the right breast and on both elbows -- and two broken ribs, which could have been caused by the CPR, the ministry said in a statement.
"There is nothing apparent from the first findings that indicate the cause of death," it added. Other tests are pending.
Jaradat will be buried Monday, his family said.
Earlier Sunday, Israeli officials had called on the Palestinian Authority to calm the Palestinian territories, where there have been large protests in recent days over the conditions of Palestinian prisoners.
There were several protests in the West Bank on Sunday.
Palestinian medical sources reported that two Palestinians were critically injured in clashes with Israeli police outside Ofer Prison in the West Bank. The Israel Defense Forces said it was looking into that report.
Israeli Prime Minister Benjamin Netanyahu's liaison with Palestinians, Yitzhak Molco, passed on the demand for calm to the Palestinian Authority, Israeli government officials said.
Four prisoners had already begun a hunger strike, and several others have joined them in recent days. In the West Bank, protesters organized rallies to support them.
All the approximately 4,500 prisoners joined the strike Sunday, the Israel Prisons Service said.
Hassan Abed Rabo, a spokesman for the Palestinian Ministry of Prisoner Affairs, said it was an "open-ended hunger strike" and "a sign of mourning" for Jaradat.
His death came amid a fury -- and a series of questions -- surrounding the death of a prisoner in 2010, referred to as "Prisoner X." Details came to light in recent days after a court document was released.
Jaradat, from a village near Hebron in the West Bank, was held for interrogation Monday by the Israeli secret service based on intelligence gathered by village residents, Israeli security sources said. The intelligence indicated Jaradat was involved in throwing stones near the Israeli settlement of Kiryat Arba in 2011. An Israeli citizen was injured in the incident.
Jaradat confessed, Israeli security sources said.
He suffered from back pains and a previous rubber bullet injury in his leg, as well as an injury from a tear gas canister that had hit his stomach, the security sources said.
While in custody, Jaradat was checked more than once by a doctor, and no medical problems were found. But after lunch Saturday, while resting, he was not feeling well, and emergency crews were called to the site. They could not save his life, security sources said.
Israel began an investigation and notified his family.
Rabo said Palestinians blame Israel for the death of "the martyr" and hold Israel responsible for the lives of all the prisoners on hunger strike.
Jaradat, the father of three, worked at a gas station, Rabo said.
"This incident should open the door to all sorts of investigation and accountabilities," said Hanan Ashrawi, a member of the Palestine Liberation Organization's executive committee. She called for Israeli prisons to be opened to the international community.
Human Rights Watch, meanwhile, called on Israel on Saturday to "immediately charge or release Palestinians detained without charge or trial for prolonged periods."
Palestinian prisoners in Israeli detention are one of many flashpoints in the Middle East conflict. Prisoners have launched hunger strikes in the past in hopes of bringing attention to their cause and pushing Israel to ease conditions or allow some prisoners to leave.
Israeli officials have pointed out that prisoners include members of extremist groups who have "blood on their hands."
In October 2011, Israel freed more than 1,000 Palestinian prisoners -- including hundreds serving life sentences for attacks on Israelis -- in exchange for one person: Israeli soldier Gilad Shalit, who had been held by Hamas for more than five years.
CNN's Kareem Khadder reported from Jerusalem; CNN's Josh Levs reported from Atlanta. CNN's Michael Schwartz contributed to this report.