I think you could say that. Hiragana is the alphabet. But it does not consist of letters like the alphabet in the western countries (A, B, C, D, E, F, ...).
It consists of syllables and vowels (a, i, u, e, o are the japanese vowels; pronunciation is not the english way but more the german or french way I would say). The only consonant which can stands alone is 'n'. Here is a link that shows the Hiragana:
http://www.kirchner-inoue.de/hiragana.gif