Top panel: Average hardness ratio (black squares) of X-ray detected AGN in clusters divided in three cluster-centric annuli, 0–1R₅₀₀, 1–2R₅₀₀ and 2–4R₅₀₀ with their standard 1σ errors. The grey line corresponds to the average hardness ratio value of field AGN (the shaded area denotes the 1σ error range). Evidently, the average HR in the 1–2R₅₀₀ area is significantly higher than in the field, at the 90% confidence level (Gehrels 1986). Bottom panel: Obscured X-ray AGN fraction in clusters. We consider as obscured AGN the objects with HR > 0 (see Sect. 4.2.2). The dashed line represents the fraction of the obscured X-ray AGN in the field (the shaded area denotes the 1σ error range). There is a significant excess of X-ray AGN in cluster outskirts, at the 2σ confidence level.