The Iraqi ministry of defence has promised a crackdown on the country's armed militias.
A ban on bearing arms could bring Iraq's army into conflict with militia
Director of operations Maj Gen Abdul Aziz Jasim said anyone carrying weapons who was not in the legitimate security forces would be treated as a terrorist.
It follows days of sectarian violence sparked by an attack on a key Shia shrine that has left at least 165 people dead since last Wednesday.
At least eight people were killed in attacks in Baghdad on Monday.
Four people died when two bombs went off just after evening prayers outside a Sunni mosque in the New Baghdad area, police said.
Another four were injured in a mortar attack on a Shia district in mainly Sunni western Baghdad.
The incidents followed the lifting of a daytime curfew imposed on Baghdad and nearby provinces.
Traffic was back to near normal and residents moved freely in the capital on Monday, as shops and petrol stations reopened.
The daytime curfew, including a 24-hour traffic ban, had been imposed amid violent reprisals to the raid on the al-Askari shrine in Samarra.
The night curfew from 2000 to 0600 will remain in place in Baghdad and the surrounding provinces of Diyala, Babil and Salahuddine.
Speaking at a news conference in Baghdad, Maj Gen Jasim said the country's security forces must stay on the highest level of alert in the wake of the recent violence.
Promising to crack down on armed groups in the street, he said anyone illegally bearing arms would be arrested and their weapons confiscated.
The day curfew has been lifted but the night curfew remains
Politicians were now working with the armed forces to prevent a repeat of the unrest, he added.
The BBC's Jon Brain in Baghdad says the announcement confirms the determination of the authorities to clamp down on the numerous private armies in Iraq.
However, if followed through the measure risks provoking armed conflict with some of the militia who have operated largely unchecked since the fall of Saddam Hussein's regime, he says.
And Iraq is a country awash with weapons. In cities such as Baghdad virtually every single adult male has a gun.
Despite the curfew measures, violence has continued across Iraq.
The attack on the al-Askari shrine sparked violent reprisals
On Sunday, 30 people died in total, 15 in a mortar assault on a Shia area of Baghdad and another 15 across the rest of Iraq, including three US soldiers.
Insurgents again attacked a Shia mosque, this time in the southern city of Basra. Reports said there was some damage but no-one was killed.
Amid fears that Iraq may slide into civil war, political leaders said they had made progress in talks to curb the violence.
Sunni clerics and one of the main Shia militias also announced that they had agreed to work together to prevent further sectarian bloodshed.
Our correspondent says the government is hoping to capitalise on the lifted curfew by restarting the process towards forming a new coalition government.
There appears to be a real determination among political leaders, at least for now, to present a united front and prevent a slip to civil war, he says.