Thousands of Shia militia loyal to the powerful cleric Moqtadaal-Sadr have paraded through the streets of Baghdad, raising sectarian tensions amid continued fighting in areas of Iraq.
The cleric, whose Mehdi Army fought the US in Iraq for years, had called for a military parade across the country.
Correspondents say the show of force will be seen as a very disturbing development by the Baghdad government.
Sunni extremists have seized control of large swathes of territory across Iraq.
On Saturday, officials admitted that the militants - led by jihadist group Isis - had seized a strategically important border crossing to Syria, near the town of Qaim, killing 30 troops after a day-long battle.
The capture of the crossing in western Iraq could help Isis transport weapons and other equipment to different battlefields, analysts say.
Thousands of largely Shia Iraqis have volunteered to fight Isis, urged on by a call from the country's highest Shia religious authority, Grand Ayatollah Ali al-Sistani.
But the BBC's Jim Muir, in northern Iraq, says the impressive-looking parade of men in battle fatigues accompanied by serious military hardware will only raise sectarian tensions at at time when the government is under pressure to rally the country together against the extremists.