The autopsy of a Palestinian teen slain in an alleged Israeli revenge attack shows the boy was burned to death while he was still alive, according to Palestinian authorities.

The day after thousands attended the funeral of 16-year-old Mohammed Abu Khdeir in East Jerussalem, the Palestinian attorney general said Saturday the boy had suffered burns to "90 percent of his body."

"The results show he was breathing while on fire and died from burns and their consequences," Abdelghani al-Owaiwi told the Associated Press.

Palestinians have accused Israeli extremists of beating and torching Abu Khdeir, who was discovered in a forest ditch in West Jerusalem on Wednesday morning, in an apparent revenge attack for the abduction and killing of three Israeli teens in the West Bank who were buried hours before the Palestinian boy disappeared.

Israeli police are conducting an investigation, and are looking into the possibility the Abu Khdeir was slain in a family honor killing or in a nationalistically motivated attack, local media reported.

Widespread riots and clashes between Palestinian protestors and Israeli police in the East Jerusalem neighborhood of Shuafat ensued following news of Abu Khdeir's death.

Mourners of slain Palestinian teen Mohammed Abu Khdeir at his funeral in Jerusalem on Friday. Photo via AP/Mahmoud Illean

In a separate incident, a video released by television station Palestine Today on Thursday shows Israeli police brutally beating Abu Khdeir's counsin, 15-year-old Tariq Abu Khdeir, who is a U.S. citizen from Florida visiting relatives in Palestine.

The screen text reads: "Exclusive to Palestine Today, video shows occupation soldiers and settlers savagely attack a Palestinian youth in Shuafat."

Another video uploaded to YouTube seemingly corroborates the footage of Tariq's beating, which was reportedly conducted in his uncle's yard in Shuafat.

Human Rights Group Addameer has released graphic photos of Tariq's swollen and bruised face. The group says Tariq was one of 11 Palestinians beaten and arrested that night and is currently in detention without charge, and has been denied medical attention. The teen faces trial on Sunday in the Court of First Instances in Jerusalem.

Tariq Abu Khdeir, after his incarceration by Israeli authorities. Photo provided to Addameer by and published with the consent of the Abu Khdeir family

The U.S. Consulate did not immediately comment on the reports.

Israeli police told the Associated press that the boy had attacked officers and resisted arrest. He was found to be in possession of a slingshot when he was detained along with six other demonstrators, some of who were armed with knives.

The violence continued into the weekend, spreading to towns in northern Israel where protestors hurled rocks and firebombs at police who returned fire with tear gas and stun grenades, Israeli police said. At least 20 people were arrested on Saturday.

Tensions between Palestine and Israel have escalated since the three Israeli settler youth were kidnapped while hitchhiking in the West Bank. The Israeli Defence Force subsequently launched a massive 18-day operation to search for the teens, which including numerous aerial bombings and raids on over 2,000 Palestinian buildings. At least five Palestinians were killed during the campaigned dubbed by the IDF as "Operation Brother's Keeper."

Israel has blamed Islamic militant group Hamas for the deaths of the three teens whose bodies were discovered on Monday nearthe Palestinian village of Halhul, in the southern West Bank. Marwan Kawasme and Amer Abu Aysha, the two Hamas members identified by Israel as the primary suspects, have been missing since the teens first disappeared on June 12.

Hamas praised the kidnappers but stopped short of claiming responsibility.

Palestinian Authority President Mahmoud Abbas condemned the kidnapping and killing of the Israeli boys and urged both sides to "refrain from violence."

But on Monday night, a16-year-old boy, Yusef Abu Zaga, was killed by live fire as demonstrators met with the Israeli military in the West Bank city of Jenin. Three other Palestinians were arrested in the clash.

Several other reprisal attacks on Palestinians were also reported that night.

The Israeli army said it launched several air strikes in Gaza on Monday night against target sites occupied by Hamas. Three Palestinians were injured in the strikes, among them an infant.

VICE News' Olivia Becker and Dylan Collins also contributed to this report.