regular expressions with the Cyrillic alphabet?

I am currently writing some validation that will validate inputted data. I am using regular expressions to do so, working with C#.

Password = @"(?!^[0-9]*$)(?!^[a-zA-Z]*$)^([a-zA-Z0-9]{6,18})$"

Validate Alpha Numeric = [^a-zA-Z0-9ñÑáÁéÉíÍóÓúÚüÜ¡¿{0}]

The above work fine on the latin alphabet, but how can I expand such to working with the Cyrillic alphabet?