Residents of Vavuniya were alarmed by an unexpected patrol by Special Task Force troops around the town while Deepavali celebrations were ongoing on Sunday.
In some places the troops stopped their patrol bikes and questioned residents.
Residents said patrols and search operations were happening more and more frequently in the district, with ad-hoc check points set up where they had previously been dismantled.
House-to-house searches by Sri Lankan soldiers were also reported in the district earlier this month.