  Let $G$ be a connected, reductive group over a non-archimedean local field
$F$. Let $\breve F$ be the completion of the maximal unramified extension of
$F$ contained in a separable closure $F_s$. In this article, we construct a
Tits group of the affine Weyl group of $G(F)$ when the derived subgroup of
$G_{\breve F}$ does not contain a simple factor of unitary type. If $G$ is a
quasi-split ramified odd unitary group, we show that there always exist
representatives in $G(F)$ of affine simple reflections that satisfy Coxeter
relations (which is weaker than asking for the existence of a Tits group). If
$G = U_{2r}, r \geq 3,$ is a quasi-split ramified even unitary group, we show
that there don't even exist representatives in $G(F)$ of the affine simple
reflections that satisfy Coxeter relations.
