The 63-year-old politician, who retained his Northern Angamai-II seat for the fifth time in a row, became chief minister for the first time on March 6, 2003, and then again on March 12, 2008.
Rio's NPF, other Naga regional parties and the state unit of the BJP had formed the Democratic Alliance of Nagaland (DAN), a coalition which won the 2003 state elections, bringing the 10-year-long rule of the Congress in the state to an end.
He was elected as president of Kohima District Youth Wing in 1974 and became the acting president of the UDF youth wing in 1976-77.He was elected as area council chairman of Northern Angami in September, 1984.
After winning in the 1993 assembly election, Rio became Minister for Works and Housing as Jamir became the chief minister again.
More From This Section
He was appointed Home minister after the 1998 election, but shortly before the next assembly poll resigned from the Jamir led Congress ministry on September 20, 2002, accusing the chief minister of blocking a negotiated settlement on the vexed Naga issue.
Rio also resigned from the membership of the assembly and the Congress on November 7, 2002. He became chief minister after winning the 2003 election.
His party emerged as the single largest party in the ensuing elections and Rio, as the leader of DAN, was invited by the governor to form the government on March 12, 2008.
Rio had a providential escape on May 30, 1995 when Naga insurgents tried to assassinate him.
Born on November 11, 1950, the NPF leader was educated at the Baptist English School, Kohima and Sainik School in Purulia in West Bengal. He did his higher education from St Joseph College, Darjeeling and graduated from Kohima Arts College.