Given an open Riemann surface M, we prove that every nonflat conformal minimal immersion \(M\rightarrow \mathbb {R}^n\) ( \(n\ge 3\) ) is homotopic through nonflat conformal minimal immersions \(M\rightarrow \mathbb {R}^n\) to a proper one. If \(n\ge 5\) , it may be chosen in addition injective, hence a proper conformal minimal embedding. Prescribing its flux, as a consequence, every nonflat conformal minimal immersion \(M\rightarrow \mathbb {R}^n\) is homotopic to the real part of a proper holomorphic null embedding \(M\rightarrow \mathbb {C}^n\) . We also obtain a result for a more general family of holomorphic immersions from an open Riemann surface into \(\mathbb {C}^n\) directed by Oka cones in \(\mathbb {C}^n\) .