The 24-year-old was initially overlooked by manager Chris Coleman, but he has been added to the squad following Sunday's withdrawals of Joe Allen and Steve Morison.
Nyatanga has won 34 international caps, but he has not featured for his country since appearing as a late substitute in the friendly defeat to Ireland in February 2011.
Liverpool midfielder Allen pulled out of the squad after aggravating a long-standing shoulder problem during Saturday's 3-1 defeat at Southampton.
Leeds striker Morison is unavailable for both matches as he recovers from a calf injury, and his place has been taken by Crystal Palace forward Jermaine Easter, currently on loan with Millwall.
Wales are looking to build on their encouraging win over Austria last month, although they are seven points behind Group A leaders Croatia and Belgium after winning only one of their opening four qualifiers.