Try to specify the ranges as unicode ranges.
I'm not very familiar with cyrillic, so I'm going to base my answer on http://en.wikipedia.org/wiki/Cyrillic_script_in_Unicode:
/[\w\u0400-\u04ff\u0500-\u052f\ua640-\ua69f\u1d2b-\u1d78]+/.exec("Слово Word");