The group called on President Muhammadu Buhari to call APC members in the state to order.
The group condemned the use of force by the military to harass and intimidate voters and opposition politicians, particularly members of the Peoples Democratic Party (PDP).
In a statement issued on Friday, December 9, by its convener, Idris Usman, it said called on President Muhammadu Buhari to warn members of the All Progressives Congress (APC) in the state against attempting to truncate democracy.
"The Civil Society Alliance for Sustainable Democracy (CSASD) wishes to call the attention of the Nigerian public and members of the International community to the present atmosphere of tension that has enveloped Rivers State, ahead of tomorrow’s legislative rerun elections in the State," the statement reads in part.
"We are alarmed by the level of deployment of members of the Nigerian armed forces, particularly the military and the ongoing use of same, to harass and intimidate opposition politicians and the innocent citizens of Rivers State.
"The last few hours have witnessed some arrest of members of the opposition PDP and vocal non-partisan citizens or what the security agents have described as ‘order from above’
"It is sad to witness the desperate dimension that politicians belonging to the ruling federal government have taken this election into, which has now practically frozen the freedom of the people of the State, only a day after the national leadership of the APC, came to openly instigate violence at the party’s campaign in Port Harcourt.
"We are therefore calling on President Buhari to immediately call members of his party, many of who have no legitimate business, but have relocated to Rivers, to order. We also want to remind everyone involved in the ongoing attempt to truncate democracy and cause arm on the innocent people, that the world is watching and we shall ensure that justice is served to everyone through legitimate means at the appropriate time."
Some political parties have also accused INEC of bias in the conduct of the election.