  A series of layered nickel-based LaO$_{1-x}$F$_x$NiAs compounds with x=0 to
0.15 are synthesized by solid state reactions. The pure LaONiAs exhibits bulk
superconductivity with Tc $\sim$ 2.75 K. Partial substitution of oxygen by
fluorine increases the transition temperature to $\sim 3.8$ K. The
LaO$_{0.9}$F$_{0.1}$NiAs sample shows a sharp superconducting transition and a
sharp specific heat jump at the critical temperature. The magnitude of the
specific heat jump is much larger than that expected from the weak-coupling BCS
theory, indicating that this superconductor is in the strong coupling regime.
Furthermore, the temperature dependence of the specific heat deviates strongly
from the theoretical result for the single-band s- or d-wave superconductor,
but shows some character of a multi-gap system.
