In a statement, they said Muslims and Christians are subjected to hate speech, discrimination, attacks and acts of violence throughout the country frequently.
More than 350 violent attacks against Muslims and over 150 attacks against Christians have been reported in the last two years, they said.
This violence is fuelled by the atmosphere of impunity, UN Special Rapporteur on freedom of religion or belief Heiner Bielefeldt said.
Impunity and inadequate response from the police and judicial authorities aimed at protecting the lives, physical security, the property and places of worship of these communities may encourage further attacks and a risk of spiralling violence, he warned.
More From This Section
The Special Rapporteur on extra judicial, summary or arbitrary executions, Christof Heyns, called on authorities to take urgent and firm measures to bring the perpetrators of killings to justice, and ensure the immediate adoption of robust protective measures.
They say that hate statements by Buddhist extremist groups have contributed to spread a climate of fear among Sinhala Buddhists, who constitute the majority population in Sri Lanka, and resentment towards minorities.
Nationalist Buddhist group BBS or the Forces of Buddhist Power led by Galagodaatte Gnanasara was accused of being behind the anti-Muslim riots that began on June 15.