Match word containing characters beyond a-zA-Z

I'm trying to match words containing characters beyond a-zA-Z. The
problem is that words like

prästgården
treść

are not recognized as words. If I match \v(\w+) on these words,
prästgården is matched three times and treść is matched only at the
beginning:

prästgården
^^ ^^^ ^^^^
treść
^^^

So the problem is that characters like å are not recognized as a
character. Checking the words with [:alpha:] proves this, it does
not match any of the characters åść. :h regex tells me that
[:alpha:] matches *letters*. For me å is a letter, not so for vim.

How to convince vim to treat characters like åść as letters? On [1]
it was suggested to resort to Perl. But I can hardly believe that
it's not possible natively in vim.

VIM - Vi IMproved 7.3 (2010 Aug 15, compiled Dec 27 2012 21:21:18)
Included patches: 1-762
Debian GNU/Linux
LANG=en_GB.UTF-8

Marco


[1] http://unix.stackexchange.com/questions/60481/match-word-containing-characters-beyond-a-za-z