According to Sri Lankan government figures, over 20,000 people are missing due to various conflicts, including the three-decade brutal war with Lankan Tamils in the north and east, which claimed at least 100,000 lives.
The joint student organisation of the Jaffna University in a statement expressed solidarity with the shutdown.
However, the protests were unsuccessful in Vavuniya, Amapara and Trincomalee districts.
In June, an alleged mass grave was accidentally discovered at Kokkuthuduvai by the National Water Board workers while carrying out digging activities for a development project in the area.
On July 6, the Mullaitivu magistrate court supervised the digging of the alleged mass grave.
Tamil political party sources said human remains of at least 13 people were found there.
The relatives of the missing people during the separatist armed conflict have demanded an international investigation into the grave.
The Liberation Tigers of
Mullaitivu was a nerve centre of the LTTE as they ran a parallel state before May 2009 when they were defeated by the Sri Lankan military.