There is a way to import them but they lose quality as advanced transparency seems to be unsupported:
1) Drag and drop the SVG file into an empty drawing area.
2) Export it as .shape
:
File -> Export...
Then select "By extension" and save the file as .shape
. Then a dialog will appear. Choose the default size in there.
3) Import it:
F9 -> NEW -> SVG Shape (select the file)
That's it. If you want to import more advanced drawings, I suggest you to try different formats, for example, PNG are imported really nicely (but of course are not vectors).
Hope it helps (and I hope DIA team implements more advanced SVG support).