We present results from an XMM-Newton observation of the nearby Seyfert 2 galaxy NGC 5643 .
The nucleus exhibits a very flat X-ray continuum above 2 keV , together with a prominent K _ { \alpha } fluorescent iron line .
This indicates heavy obscuration .
We measure an absorbing column density N _ { H } in the range 6–10 \times 10 ^ { 23 } cm ^ { -2 } , either directly covering the nuclear emission , or covering its Compton-reflection .
In the latter case , we might be observing a rather unusual geometry for the absorber , whereby reflection from the inner far side of a torus is in turn obscured by its near side outer atmosphere .
The nuclear emission might be then either covered by a Compton-thick absorber , or undergoing a transient state of low activity .
A second source ( christened ” X-1 ” in this paper ) at the outskirts of NGC 5643 optical surface outshines the nucleus in X-rays .
If belonging to NGC 5643 , it is the third brightest ( L _ { X } \sim 4 \times 10 ^ { 40 } erg s ^ { -1 } ) known Ultra Luminous X-ray source .
Comparison with past large aperture spectra of NGC 5643 unveils dramatic X-ray spectral changes above 1 keV .
We interpret them as due to variability of the active nucleus and of source X-1 intrinsic X-ray powers by a factor \geq 10 and 5 , respectively .