  We study the local properties of positive solutions of the equation $-\Delta
u=u^p-m|\nabla u|^q$ in a punctured domain $\Omega\setminus\{0\}$ of
$\mathbb{R}^N$ or in a exterior domain $\mathbb{R}^N\setminus B_{r_0}$ in the
range $\min\{p,q\}>1$ and $m>0$. We prove a series of a priori estimates
depending $p$ and $q$, and of the sign of $q-\frac {2p}{p+1}$ and $q-p$. Using
various techniques we obtain removability results for singular sets and we give
a precise description of behaviour of solutions near an isolated singularity or
at infinity in $\mathbb{R}^N$.
