Developments in Greece and Spain could lead first to rating reviews and then to rating actions on all 17 countries in the euro zone, Moody's Investors Service announced Friday.

Greece will conduct snap parliamentary elections on June 17, and Spain agreed to accept as much as €100 billion ($125 billion) in a bailout of its cash-strapped financials sector on Saturday.

Any heightening in the risk of a possible Greek euro-area exit could lead to more rating pressures in the euro zone, Moody's said.

A rising risk of a Greek euro-area exit would have its greatest immediate impact on the credit standing of Cyprus, Ireland, Italy, Portugal, and Spain, Moody's said.

If Greece were actually to exit the euro zone, then Moody's would review all 17 of the relevant sovereign ratings, the credit-rating agency added.

Moody's made a clear distinction between Greece and Spain in its announcement. The agency said Spain's banking-system problem is primarily centered in that country, meaning -- unlike Greece -- it is not likely to be a major source of contagion for other euro-area countries, except for Italy.

Both Spain and Italy have been indirectly relying on European Central Bank funding via their banks, a reliance that has been growing in each case, Moody's said.