CPI(M) general secretary Sitaram Yechury and CPI leader D. Raja were on Friday detained at the Srinagar airport while on their way to meet party leaders and denied entry into the region.
The CPI-M condemned the detention of two leaders and said it showed the "authoritarian face of BJP government".
It said Yechury and Raja had gone to Srinagar to visit CPI(M) MLA Mohammad Yusuf Tarigami, who is ailing, and to meet the people of Jammu and Kashmir.
CPI-M called upon people to protest the "anti-democratic act of the BJP government".
Yechury had on Thursday written to Jammu and Kashmir Governor Satya Pal Malik saying he will be visiting Srinagar on Friday to meet his party MLA and other members of the party.
Congress leader Ghulam Nabi Azad was also detained at the Srinagar airport on Thursday and sent back to the national capital.
The city is under restrictions following Centre's decisions to bifurcate the state into two union territories and to repeal Article 370.
Both the Houses of Parliament passed a bill earlier this week bifurcating Jammu and Kashmir into two Union Territories and adopted a resolution revoking Article 370.