Traffic was also disrupted near the island’s main international airport as the police inspected a suspicious vehicle.
The Indian Ocean island remains under curfew and emergency security measures while the counter-terrorism operation, assisted by experts from the US, UK, Australia and UAE, is underway.
All Catholic churches have been instructed to stay closed and suspect services until security improves.
Christians in Jaffna, in the north of the country, issued a statement urging “patience and peace as the truth of these heinous crimes emerges,” adding: “our grief is never a call for retribution.”
Their appeal came as Sri Lanka’s minority Muslim community spoke of their fears about retaliation and reported online abuse and stones being thrown at Muslim homes and businesses.
Sri Lanka’s government believes that the massacre was carried out with the NTJ, previously an obscure local Islamist group, with assistance from overseas terrorism networks due to its precise and coordinated nature and the use of military-grade explosives used.