Sri Lanka's military has reintroduced all security measures in effect before a 2002 ceasefire between the government and Tamil Tiger rebels, following the assassination of one of the country's top general.
The military says that means increased road blocks and security checks at all military checkpoints immediately.
Major General Parami Kulatunga and three other people were killed near the capital, Colombo, Monday, when a suicide bomber rammed his motorcycle into the general's car.
Sri Lanka's military blamed the attack on the Liberation Tigers of Tamil Eelam rebel group, which is a U.S. State Department designated terrorist organization. But the rebels denied any involvement, saying the incident is an attempt by the government to smear their name, and to serve as a pretext for military action against them.
Sri Lanka's President Mahinda Rajapakse called the bombing an attempt by the Tamil Tigers to derail efforts to restore peace in the island nation.
An upturn in violence in Sri Lanka in recent months has brought concerns that an official ceasefire between government forces and Tamil rebels could crumble into renewed civil war.
Almost 700 people have been killed since April, more than half of them civilians.