Anti-US Shia cleric Moqtada al-Sadr has told an enthusiastic crowd of followers in Iraq to give the country's new government a chance, and resist US occupiers.

The radical cleric was making his first speech since returning to his stronghold in Najaf after nearly four years of self-imposed exile in Iran. Last month his movement secured a deal to join the new government with seven ministries and 39 seats in parliament.

He urged resistance against "occupiers of Iraq" and led chants against the US. His militia, the Mehdi Army, clashed several times with US and Iraqi forces after the 2003 US-led invasion.

At the start of his short speech, the cleric called on the crowd of thousands to chant "No, no, to America", rejecting all occupiers and denouncing Israel.

"We are still fighters," he told the crowd. "We are still resisting, we resist the occupation, militarily, culturally and all other kinds of resistance."

At 39, his black beard is now tinged with grey after his four years of self-imposed exile in Qom. The fiery, anti-US rhetoric was still there, but a more moderate and responsible note carried through al-Sadr's first big speech since he came back to Najaf.

The usually dour and scowling cleric, dressed in black turban and robes, even smiled as he led the crowd in chanting religious and militant slogans. That aside, his main message to the Iraqis was clear.

"Whatever happened between brothers happened, but that page must be forgotten and turned forever," he told them, urging them never to raise their hands against one another.