We improve the earlier restrictions on parameters of the dark matter (DM) inthe form of a sterile neutrino. The results were obtained from non-observingthe DM decay line in the X-ray spectrum of the Milky Way (using the recentXMM-Newton PN blank sky data). We also present a similar constraint coming fromthe recent XMM-Newton observation of Ursa Minor -- dark, X-ray quiet dwarfspheroidal galaxy. The new Milky way data improve on (by as much as the orderof magnitude at masses ~3.5 keV) existing constraints. Although the observationof Ursa Minor has relatively poor statistics, the constraints are comparable tothose recently obtained using observations of the Large Magellanic Cloud orM31. This confirms a recent proposal that dwarf satellites of the MW are veryinteresting candidates for the DM search and dedicated studies should be madeto this purpose.
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