  Inclusive dijet and trijet production in deep inelastic $ep$ scattering has
been measured for $10<Q^2<100$ GeV$^2$ and low Bjorken $x$, $10^{-4}<x_{\rm
Bj}<10^{-2}$. The data were taken at the HERA $ep$ collider with centre-of-mass
energy $\sqrt{s} = 318 \gev$ using the ZEUS detector and correspond to an
integrated luminosity of $82 {\rm pb}^{-1}$. Jets were identified in the
hadronic centre-of-mass (HCM) frame using the $k_{T}$ cluster algorithm in the
longitudinally invariant inclusive mode. Measurements of dijet and trijet
differential cross sections are presented as functions of $Q^2$, $x_{\rm Bj}$,
jet transverse energy, and jet pseudorapidity. As a further examination of
low-$x_{\rm Bj}$ dynamics, multi-differential cross sections as functions of
the jet correlations in transverse momenta, azimuthal angles, and
pseudorapidity are also presented. Calculations at $\mathcal{O}(\alpha_{s}^3)$
generally describe the trijet data well and improve the description of the
dijet data compared to the calculation at $\mathcal{O}(\alpha_{s}^2)$.
