In this paper we deal with the following quasilinear parabolic problem ⎧ ⎪ ⎪ ⎨ ⎪ ⎪ ⎩ (u θ)t − Δpu = λ u p−1 |x| p + u q + f, u ≥ 0 in Ω× (0, T), u(x, t) = 0 on ∂Ω × (0, T), u(x, 0) = u0(x), x ∈ Ω, where θ is either 1 or (p − 1), N ≥ 3, Ω ⊂ I R N is either a bounded regular domain containing the origin or Ω ≡ I R N , 1 < p < N, q > 0 and u0 ≥ 0, f ≥ 0 with suitable hypotheses. The aim of this work is to get natural conditions to show the existence or the nonexistence of nonnegative solutions. In the case of nonexistence result, we analyze blowup phenomena for approximated problems in connection with the classical Harnack inequality, in the Moser sense, more precisely in connection with a strong maximum principle. We also study when finite time extinction (1 < p < 2) and finite speed propagation (p > 2) occur related to the reaction power.