The Minority Rights Group International said Colombo's decision to formally withdraw from the ceasefire deal with the rebels would result in escalating violence.
The Scandinavian monitoring mission appointed to oversee the ceasefire will cease operations January 16 following the government's decision announced earlier this week.
"There is now going to be a greater void in the monitoring and reporting of human rights abuses in the conflict zone," Minority Rights Group's director Mark Lattimer said in a statement received here.
"The need for international human rights monitors is now ever more crucial," Lattimer said.
Sri Lanka has rejected previous calls for a UN rights mission here.
The rights group accused the Sri Lankan government of reducing security of key minority politicians and called on Colombo to ensure proper protection for minority political leaders.
The statement came after opposition Tamil lawmaker T.
Maheswaran was gunned down earlier this week in Colombo as h