|Thousands arrived to listen to al-Sadr speak for the first time since his return from exile [EPA]
Muqtada al-Sadr, the Iraqi Shia Muslim religious leader, has called on his followers to resist the "occupiers" of Iraq.
In his first public address since returning from self-imposed exile, he called on the newly formed government to make sure all US forces left Iraq by the end of the year as planned.
"We are still resisting the occupation through armed, cultural and all kinds of resistance, so repeat after me: no, no to occupiers," al-Sadr told a crowd of thousands outside his ancestral home in Najaf on Saturday.
"Yes, yes for Muqtada! Yes, yes for the leader!" the crowd shouted, waving Iraqi flags and al-Sadr's pictures.
David J. Ranz, the spokesman for the US embassy in Iraq, brushed off al-Sadr's remarks, saying the speech contained "nothing new".
A security agreement between Washington and Baghdad requires all US forces to be out of Iraq by the end of the year, but officials in both countries have admitted that security forces are not yet ready to protect Iraq's borders from possible invasion.
Al Jazeera's Jane Arraf in Baghdad said that al-Sadr's message specified ending the occupation as a key goal.
"He made clear reference to fighting them [the US forces] with all means necessary ... but he also made clear that this is a more disciplined Sadr organisation," she said.
"He said breaches would not be tolerated and that Iraqis would not assassinate Iraqis ... altogether a much more determined, perhaps a more disciplined Muqtada al-Sadr."
Police and al-Sadr's guards were out in force in Al-Hanana, the area of Najaf where al-Sadr's home is located, and where he spoke.
Al-Sadr gained widespread popularity among Shias in the months after the 2003 US-led invasion, and his Mahdi Army militia later battled US and Iraqi government forces in several bloody confrontations.
But in August 2008, he suspended the activities of the Mahdi Army, which once numbered in the tens of thousands, after major US and Iraqi assaults on its strongholds in Baghdad and southern Iraq in the spring.
Al-Sadr left Iraq at the end of 2006, according to his movement, and had reportedly been pursuing religious studies in the Iranian holy city of Qom. He returned to his home city of Najaf on Wednesday.
Iraq's new government, which was finally approved by parliament on December 21 after nine months of delays, includes six ministers from Sadr's bloc and the popular leader said that it must be given a chance to perform.
"The government is new, so we should give it a chance to prove it is at the service of the people," Sadr said.
Ali Al-Saffar, the deputy editor and Iraq analyst at the Economist Intelligence Unit, said that al-Sadr's remarks about the government were probably more significant than the rhetoric about resistance.
"I think Muqtada al-Sadr has realised that times have changed since he left Iraq," he told al Jazeera from London.
"Right now there isn't the sectarian warfare, the rampaging in the streets, that was going on when left. So I think he has had to moderate his tone, while at the same time staying true to the more fundamental pillars of his support base.
"The Sadrists could do very well from the democratic process - they have 39 seats in parliament and several ministries including the planning ministry, which is an important one in Iraq - and the alternative is a futile one."
Al Jazeera and agencies