Iran's opposition leader yesterday pledged to remain defiant in the face of new threats including calls by hard-liners for his execution and said he was ready to sacrifice his life in defence of the people's right to protest peacefully against the government.

Mir Hossein Mousavi’s remarks come after the worst unrest since the immediate aftermath of the disputed June presidential election. At least eight people died during antigovernment protests on Sunday, including Mousavi’s nephew.

In one of his strongest statements to date, Mousavi said he was ’’ready for martyrdom" the sacrifice of one's life for a higher cause and lashed out at the bloody crackdown the authorities are waging against the opposition.

He said the government was making more mistakes by resorting to violence and killings, and that it must accept the people's rights to hold peaceful demonstrations.

Iranian hard-liners have called for the execution of Mousavi and other opposition figures, while a previously unknown group claimed in an online posting that suicide squads were ready to assassinate opposition leaders should the judiciary fail to punish them within a week.

Iran's state prosecutor on Thursday warned opposition leaders could be put on trial if they

don't denounce this week's anti-government protests.

"I explicitly and clearly state that an order to execute, murder and imprison (opposition leaders) ... won't resolve the problem," Mousavi said in a statement on his Web site, Kaleme. "I’m not afraid to be one of the martyrs people have offered in the struggle for their just demands."

The confrontation between clerical rulers and their opponents returned to the streets in recent weeks, after a harsh crackdown immediately following the June 12 balloting all but crushed the opposition movement.

One of those killed in clashes Sunday between security forces and opposition protesters was Mousavi’s nephew, Ali Mousavi. He was gunned down but authorities claimed police didn't use firearms and said the nephew was "assassinated" by unknown assailants.

The nephew was buried Wednesday in a hastily organised ceremony that was attended by the opposition leader and other family members. Authorities had taken the body from the hospital earlier in the week in what was seen as an attempt to prevent the funeral from turning into another pro-opposition protest.

Hard-liners have become especially furious after some pro-opposition protesters chanted slogans against Supreme Leader Ayatollah Ali Khamenei a taboo in Iran, where the supreme leader is considered answerable only to god.