Moving tags from one top-level tag to another

I have about 200 tags under the top-level tag "Imported Tags". I need
to move about 150 of these to the "People" top-level tag. Although I
can select multiple tags with CTRL-Click I cannot drag them all at
once to the new top-level tag. Only one of them gets dragged. And as
each time I move a tag F-Spot takes about a full minute (because I
have over 6000 photos), if I do them one-by-one I will be here hours.
Is there a quick way to move several tags at once?

Thanks in advance.

Dotan Cohen