In an interview with the hardline newspaper Jomhuri Eslami, the head of the Tehran Revolutionary Court, Gholamhossein Rahbarpour, said two of the sentences had been confirmed by the Supreme Court.

The week-long unrest - the worst in Iran since the aftermath of the 1979 Islamic revolution - was sparked when police and armed right-wing Islamic vigilantes attacked a peaceful student demonstration against the banning of a reformist newspaper.

The riots left three people dead according to official figures, while students and moderate newspapers said at least five people were killed and dozens injured.

Middle East correspondent Jim Muir reports

Hardline leaders, who are engaged in a power struggle with the moderates allied with President Mohammad Khatami, ordered hundreds of arrests and officials said those found responsible would be dealt with harshly.

Others 'under investigation'

Judge Rahbarpour said the four people, whom he did not name, had organised links with certain political groupings, which is why the verdict concerning them had not been announced immediately.

He also held out the possibility of further death sentences among the 1,000 arrested during the protests.

"There are other dossiers with heavy punishments under investigation," he said.

The judge said about 1,000 suspects had been handed over to the special court - originally created to punish collaborators with the pre-revolutionary regime.

Of these, 20 had been cleared of any wrongdoing, and investigations were continuing against the others.

The judge did not specify the charges but he suggested the harshest sentences were aimed at those blamed for inciting the riots.

"The people who laid the grounds ... for the riots ... are definitely criminals," he said.

Israel spying case

Speaking about another controversial case involving 13 Iranian Jews arrested on charges of spying for Israel, Judge Rahbarpur said that the courts had evidence that proved their guilt.

The judge said that as the crimes had been committed in the southern province of Fars, the files had been handed to the court in Shiraz.

If convicted, the defendants face a near certain death sentence under a 1996 law which calls for capital punishment for those found guilty of spying for Israel or the United States.