The official declaration was made by Kohima district Deputy Commissioner Rovilatuo Mor during a campaign for Smoke Free Kohima City.
Guidelines for adherence by public and enforcement by the district administration and police would be brought out soon, Mor said.
The campaign in which students of 22 schools took part was organised by District Tobacco Control Cell under the Department of Health and Family Welfare.
The students were carrying placards bearing anti-tobacco slogans.