Nine cities from eight northeastern states have found place in Swachh Survekshan-2017, with Sikkim's capital Gangtok emerging as the region's cleanest city.The report of the evaluation, conducted in 434 cities and towns across the country, was released by Union Urban Development Minister M. Venakaiah Naidu in New Delhi on Thursday. Gangtok ranked 50 with a score of 1,414.Mizoram capital Aizawl and Manipur capital Imphal ranked 105 and 122, respectively, followed by Assam's main city of Guwahati at 134, Nagaland capital Kohima (208), Arunachal Pradesh capital Itanagar (216), Meghalaya capital Shillong (276), Assam's commercial city Silchar (280) and Tripura capital Agartala (290).An official of Tripura's Urban Development Department said that cities were evaluated on five parameters -- waste collection, solid-waste management, construction of toilets, sanitation strategies and behaviour change communication."The rankings are based on the data provided by municipal bodies, independent assessors and feedback from people," the official added.Northeast India's largest city Guwahati which was ranked 50 in 2016, is ranked 134 this time and is the fourth cleanest city in the region after Gangtok, Aizawl and Imphal.In 2016, Agartala was ranked 33rd, Shillong 53rd and Itanagar 71st while Kohima was not listed in 2016.Agartala Municipal Corporation Mayor Prafulla Jit Sinha said: "We did not accept various schemes under the Swachh Bharat Mission that's why our position was lowered this time."