Regular expression

Hello,

Case insensitive pattern matching gives strange results for non-ascii
character (such as UTF-8 encoded cyrillic letters):
test=# select 'б' ~* 'Б' ;
?column?
----------
f
(1 row)
( 'б' and 'Б' are lower and upper case variants of cyrillic 'B')

at the same time:
test=# select 'б' ilike 'Б' ;
?column?
----------
t
(1 row)

(PG 8.3 on Linux, UTF-8 locale)

Also, what could be the reason for that cyrillic letters are not treated by
regexp engine as the part of [:alpha:], [:alnum:], \w etc. classes? Or they
never meant to be?