NEW DELHI — Fears of a broad crackdown against rights activists in Sri Lanka have been heightened after the Sri Lankan police recently arrested two prominent human rights advocates and a woman who has made a public campaign of finding her missing son.

The arrests took place just as the United Nations Human Rights Council considers starting an inquiry into possible war crimes committed by government forces and separatists during Sri Lanka’s 26-year civil war.

Ruki Fernando, one of Sri Lanka’s most prominent human rights activists, and the Rev. Praveen Mahesan, a Roman Catholic priest and the former director of the Jaffna-based Center for Peace and Reconciliation, were detained around 10 p.m. on Sunday by Sri Lanka’s Terrorist Investigation Department in Kilinochchi, a former rebel stronghold.

The Sri Lankan police said the two activists were being held under the country’s antiterrorism laws. “They have been arrested on charges of creating communal disharmony and inciting racial hatred,” said Ajith Rohana, a police spokesman. He said the two would be taken to Colombo, the capital, for further interrogation.