Jerusalem (AFP) - Israeli Prime Minister Benjamin Netanyahu on Monday telephoned the father of an east Jerusalem teenager who was kidnapped and killed last week in a suspected revenge attack by Jewish extremists.

The brutal murder of Mohammed Abu Khder, 16, on Wednesday has sparked days of clashes between angry protesters and riot police which began in annexed east Jerusalem and have since spread to Arab towns in Israel.

In a statement, Netanyahu's office said he had spoken with the teenager's father, Hussein Abu Khder, to offer his condolences and express his outrage over the "abhorrent" murder a day after the security forces confirmed arresting six Jewish extremists on suspicion of involvement.

"I would like to express my outrage and that of the citizens of Israel over the reprehensible murder of your son," Netanyahu told him.

"We acted immediately to apprehend the murderers. We will bring them to trial and they will be dealt with to the fullest extent of the law," he said.

"We denounce all brutal behaviour. The murder of your son is abhorrent and cannot be countenanced by any human being."

The family, who live in Shuafat in east Jerusalem, contacted police just before dawn on Wednesday to say they believed their son had been kidnapped.

His body was discovered shortly afterwards in a forest in west Jerusalem, with initial post-mortem results indicating he was burned alive.

Honenu, a legal organisation which defends right-wing Jewish extremists, has confirmed its lawyers are representing six people -- three of them minors.

The grisly attack was believed to be in revenge for the abduction and murder in the occupied West Bank last month of three Israeli teenagers, two of them 16, which Israel has blamed on Islamist movement Hamas.