Families of the disappeared defied military and police intimidation to hold a mass rally in Vavuniya on Thursday.
"Where! Where! Where are our children?" families from all five districts of the North chanted, marching through the town.
The families also called for justice for their disappearances and condemned the actions and responses of Sri Lankan president Gotabaya Rajapaksa.
The protesters were joined by Tamil politicians including parliamentarian Sivasakthi Ananthan and other members of the TNA and TNPF.