HANOI, Oct 7 (Reuters) - Independent online air quality index monitor AirVisual said on Monday it is under "coordinated attack" to discredit the company after its data showed Hanoi has at times recently topped the list of the most polluted cities in the world. Air pollution in Hanoi and other major cities in Vietnam has hit its worst-ever levels, with the government's Environment Administration last week warning people to limit outdoor activities. Pollution could become a key political issue in Vietnam, where protests have been held against the degradation of the environment. "AirVisual has received abusive and threatening messages posted on Facebook and on the Apple App Store and Google Play Store," it said in a statement on Monday. "Consequently, the AirVisual apps and Facebook page are currently no longer accessible in Vietnam," it said. AirVisual has been among the most downloaded apps in Vietnam. AirVisual said its data has helped raise awareness of air quality issues in Vietnam, but this also made it the target of a campaign to discredit the company. AirVisual said it is working with Apple, Google and Facebook to confirm that it has been unfairly attacked, and to make the AirVisual apps available again in Vietnam. We've got more newsletters we think you'll find interesting. Please try again later. The email address you have provided is already registered. The government last week blamed the pollution on low rain levels and farmers burning rice crop remnants after the harvest to prepare for new plantings. Coal is also widely used for power generation in the country. (Reporting by Khanh Vu, Editing by Ed Osmond)
The company behind popular air pollution app AirVisual has said it has been the target of a " coordinated attack " , with " abusive and threatening " messages posted on Facebook , as well as the Apple ##oi website and mobile app Store . AirVisual said it came after company data revealed Hanoi was , at times , the world 's most polluted city , prompting it to take down its mobile app and Facebook page . Hanoi 's Environment website recently warned residents to limit outdoor activity .