New Delhi, Dec. 9 -- India on Monday advised its citizens travelling to China to be careful and sought reassurances from Chinese authorities that its nationals will not be targeted or harassed at Chinese airports in the wake of the detention of a woman from Arunachal Pradesh at Shanghai airport. New Delhi had earlier lodged a strong protest with Beijing after the woman from Arunachal Pradesh was detained at Shanghai airport on November 21 by authorities who declared her Indian passport invalid. Expressing concern at the incident, external affairs ministry spokesperson Randhir Jaiswal told a weekly media briefing that the ministry "would advise Indian nationals to exercise due discretion while travelling to China or while transiting through the country". He added, "We expect the Chinese authorities to provide assurances that Indian citizens transiting through Chinese airports will not be selectively targeted, arbitrarily detained or harassed, and that regulations governing international air travel would be respected by the Chinese side." The woman, Pema Wangjom Thongdok, said she was held by immigration officials at Shanghai airport for more than 18 hours, made fun of, and asked to apply for a Chinese passport. Thongdok lives in the UK and was on her way to Japan for a vacation, with a three-hour layover in Shanghai. She had a Japanese visa but wasn't allowed to board a China Eastern Airlines flight. Her ordeal ended only after Indian officials intervened, she said. People familiar with the matter described the incident as unfortunate, especially at a time when India and China have resumed direct flights after a gap of nearly five years as part of the normalisation of relations after the prolonged military face-off on the Line of Actual Control (LAC). Such moves lead to unnecessary obstructions to the process of normalisation, they said. New Delhi has consistently rejected Beijing's claims on Arunachal Pradesh, and said the northeastern state is an integral and inalienable part of the country. After the incident involving Thongdok, the external affairs ministry issued a strong demarche to the Chinese side in Beijing and in New Delhi, and the Indian consulate in Shanghai took up the matter with Chinese authorities....