Moody's has warned the outlook for Germany's AAA credit rating is negative, citing risks to the country from a possible Greek exit and wider eurozone troubles.

The eurozone's other top-rated economies, the Netherlands and Luxembourg, were also put on negative outlooks. France and Austria lost their AAA ratings earlier this year.

A negative outlook from Moody's reflects a higher risk the actual rating will be cut at some point in the next two years.

Moody's said there was an increased chance Greece could leave the eurozone, which "would set off a chain of financial sector shocks". It warned policymakers could only contain these shocks at a very high cost.

"This burden will likely fall most heavily on more highly rated member states if the euro area is to be preserved in its current form," it said.

However, the German Finance Ministry said the country would remain strong, and Moody's was focusing on short-term risks, the BBC reports.

"By means of its solid economic and financial policy, Germany will retain its 'safe haven' status and continue to play its role as the anchor in the eurozone responsibly," the ministry said.

Standard & Poor's and Fitch currently have Germany on an AAA rating with a stable outlook.

The outlook downgrades from Moody's come as worries over the eurozone crisis pushed the yields on Spanish and Italian debt to record euro-era highs yesterday.