The order suspending 66-year-old Rio from the primary membership of the party with immediate effect was taken last evening, a party statement here said.
The suspension order said that he had "indulged in anti-party activities in order to dislodge the party's government so that he could regain the position of the chief minister."
Rio was the chief minister of Nagaland for three consecutive terms since 2003. He was elected to the Lok Sabha in 2014.