The families have been seeking information on their missing family members from the government, claiming that there was no response from authorities.
The protesters, sitting in Kilinochchi for the last 100 days, said the government must act with urgency to provide them answers.
"We want justice where are our children?" they said.
The governor of the northern province informed the protesters that President Maithripala Sirisena would appoint a committee next week to look into the problem of the relatives of the missing people.
More From This Section
Due to the ongoing devastating flood in the country's southern region, Sirisena would meet the protesters within two weeks, the governor said.
Protesters said that they were unwilling to appear before yet another committee but would meet Sirisena.
Tamil rights groups want the government to probe the cases of all those disappeared and hold the culprits accountable.
A government-appointed probe committee in 2013 said that over 19,000 had disappeared in the country with over 5000 of them belonging to the government troops.
In August last year, Sri Lanka's Parliament unanimously approved a bill to set up an office to help find some 65,000 people reported missing during the country's civil war with the LTTE (1983-2009), and clarify the circumstances under which they disappeared.