Official sources said the office of Apni Party, headed by Altaf Bukhari, was also closed for the day as a precautionary measure.
National Conference chief spokesman Tanvir Sadiq claimed that he has been placed under house arrest.
"I have been detained at home, which was completely unnecessary. I needed to leave for some work, but policemen outside my gate prevented me from doing so. This is unwarranted and illegal," Sadiq said in a post on X.
He also posted a picture showing police personnel outside the gate to his residence in Hassanabad area of the city.
"August 5 is and will always remain unconstitutional and illegal. On August 5, 2019, the BJP betrayed the people of Jammu and Kashmir. By ignoring the Constitution, the BJP undermined the constitutional, moral, ethical, and legal relationship with the J&K," the NC spokesman added.
The Centre on August 5, 2019 revoked Article 370 of the Constitution which provided special status to Jammu and Kashmir within the Indian Union.
The Centre also brought the Jammu and Kashmir Reorganization Act that bifurcated the erstwhile state into two union territories of Ladakh and Jammu and Kashmir.
People's Conference president Sajad Gani Lone said August 5 will be a reminder of "complete disempowerment of Kashmiri people".
"August 5 will always be an ugly reminder of the complete disempowerment of the Kashmiri people. Five years on there is no elected Assembly and the locals have no say in running their own affairs. And sadly there aren't enough powerful voices in the country to seek questions as to why J and K has been selectively targeted for such humiliating existence," Lone posted on X.