Google Inc. (GOOG) is reporting an unusual drop in traffic to its sites in China, and an Internet monitor said the search engine’s services are being blocked in the world’s most populous nation.

Google’s Transparency Report, which measures traffic to its sites around the world, is showing a bigger-than-typical plunge in China traffic today. The company’s services -- including mail, maps and document storage -- are being blocked in China, according to Greatfire.org, a website that monitors Internet activity and access in China.

China’s government, which kicked off the 18th Chinese Communist Party Congress this week to appoint a new generation of leaders, maintains media regulations that let it block websites that it deems out of compliance with those rules. Google said in 2010 that it would not comply and shuttered its local search page, redirecting users to a Hong Kong site.