In this article we study local and global properties of positive solutions of −∆mu = |u| p−1 u + M |∇u| q in a domain Ω of R N , with m > 1, p, q > 0 and M ∈ R. Following some ideas used in [6,7], and by using a direct Bernstein method combined with Keller-Osserman's estimate, we obtain several a priori estimates as well as Liouville type theorems. Moreover, we prove a local Harnack inequality with the help of Serrin's classical results.