The de-escalation of the fighting suggests negotiations are ongoing between the armed forces and rebels
"A curfew will be imposed until things settle down," he told reporters in Colombo.
Government officials also said major social media networks and messaging apps, including Facebook and WhatsApp, have been blocked inside the country to prevent misinformation and rumours.
But the BBC says that it has received sporadic social media messages from people in Sri Lanka. The extent to which the messaging services are affected is unclear so far.