Iraq announced a curfew, weapons ban, border closings and other security measures to clamp down ahead of next weekend's key constitutional referendum and prevent insurgent attacks.
Sunni Arabs geared up their campaign to defeat the measure at the polls.
On Thursday - two days ahead of the vote - a nationwide nighttime curfew will begin and nobody will be able to carry weapons in public, even if they are licensed, Iraq's interior minister said.
On Friday evening, police will bar travel between provinces. International borders, airports and ports also will be closed.