A leading pollution-monitoring app returned to Apple and Google Play stores in Vietnam on Wednesday, days after it was removed having been bombarded with negative comments online.

The Swiss-based company AirVisual said this week it was the target of a “coordinated campaign” of abuse after publishing data showing several days of “unhealthy” pollution levels in Hanoi.

The data prompted a blitz of negative comments on AirVisual’s app and Facebook pages from Vietnamese users accusing the company of publishing misleading data to sell its products.

Online abuse is rampant in Vietnam, where state-aligned netizens frequently attack activists and sites deemed anti-government.

The app and AirVisual’s Facebook page were taken down, but the company said Wednesday the service was back up in the country after its pages were flooded with positive messages from Vietnamese users instead.

The support showed the “strength and resolve of the community in Vietnam to raise awareness about the environment and tackle the air pollution problem”, the company said in a statement.