Position of all identified O stars or O star candidates in the search field centred on NGC 6618 and NGC 6618 PG, save one. The O star candidate 2MASS J18182392-1721517 is located outside of the field shown. Identified member stars are shown with white plusses; those that are O star (candidates) as magenta circles. O star (candidates) that are not identified as member of NGC 6618 are shown as blue circles. For context, we show the DSS2 B, R and I colour image and the Very Large Telescope Survey Telescope OmegaCAM image (ESO/INAF-VST/OmegaCAM). The inset zooms in on the centre of NGC 6618. The green cross in this inset indicates the determined cluster centre. With dashed circles the location of the emission nebulae and open cluster(s) are shown. The bars denoting physical size correspond to ∼0.2 deg (6 pc) and ∼0.03 (1 pc).