The riots came three weeks after suicide bomb attacks on three churches and three luxury hotels in Colombo, killing 258 people. The April 21 attacks were blamed on a local jihadi group.
This weekend Sri Lanka celebrates Vesak which marks the birth, enlightenment and the passing of the Buddha over 2,500 years ago on Saturday and Sunday.
The most important Buddhist celebration coincides this year with the country marking a decade since ending a 37-year-separatist by annihilating the entire leadership of Tamil Tiger guerrillas.
The head of the Tamil Tigers, Velupillai Prabhakaran was killed 10 years ago Saturday while the government declared an end to the war a day later.
President Maithripala Sirisena and Prime Minister Ranil Wickremesinghe are due to attend several ceremonies in and around Colombo on Sunday to pay tribute to over 28,000 security personnel who died during the nearly four-decade-long war.
The minority Tamil community too is expected on Saturday to pay tribute to their war dead, including Tiger rebels at low-key ceremonies in the northeastern district of Mullaittivu where the final battles were fought.
Army chief Mahesh Senanayake said security forces will not obstruct any war remembrance by the Tamils. Under the previous regime, any war remembrance by Tamils was outlawed.
Police said security would remain tight over the weekend for a major Buddhist festival as well as the 10th anniversary of the ending of the country's decades-long Tamil separatist war.