Sri Lanka's National Security Council on Monday announced plans to impose a "conditional state of Emergency" from midnight.
A press release from the President's media unit referred to articles on combating terrorism as the basis for the action.
It said the measures would target terrorism and would not limit freedom of expression.
The decision comes ahead of a national day of mourning scheduled for Tuesday for the 290 people killed in the Easter Sunday attacks at three luxury hotels and three churches besides two other locations.
Sri Lankan outfit National Thowheed Jamath blamed for bombings