RAMALLAH, Palestinian Territories (AFP) - A Palestinian teenager, whose abduction and murder sparked three days of violent protests, was burned alive, according to initial post-mortem findings reported by Palestinian media on Saturday.

Mohammed Abu Khder, 16, was kidnapped from the Shuafat neighbourhood of Arab east Jerusalem on Wednesday and his burnt body was found hours later in a west Jerusalem forest, in an attack Palestinians believe was carried out by Jewish extremists.

Pathologists found the presence of smoke in his lungs, meaning he was alive while he was being burned, the Maan news agency quoted Palestinian attorney general Mohammed Aluweiwi as saying.

Abu Khder also suffered a head wound, but that did not cause his death, Mr Aluweiwi added.

Israeli police said on Saturday that they still could not confirm whether Abu Khder's murder was a revenge attack for the murder of three Israeli youths in the occupied West Bank last month.

A spokesman told AFP police were investigating "all possibilities", noting there was a gag order on all details of the investigation.

The teenager's funeral, which was joined by thousands of mourners on Friday, was accompanied by clashes across Israeli-annexed Arab east Jerusalem, the third straight day of violence since the discovery of his body.

Disturbances spread to the Arab towns of Taibe in northeastern Israel and Jaljulia and Qalansuwa in the centre.