In what part of the world, that uses Latin alphabet, will you find the letter "R" used as a vowel?

Need a hint??
Let me think! Are you fast enough for this "BRZO" ?

Ah ah, Mozart! Your subtle hint points towards Serbian, where the word "brzo" means "quickly" or "fast"!

Yes Bosnian & Serbian, right answer Colin, congrats. Look here

"It should also be mentioned the that letter "R" stands as both a consonant and a vowel. It is considered a vowel when surrounded by two other consonants. For example in the words: brzo (quick), trn (thorn), mrk (dark), vrlo (very)".