China's Foreign Ministry said on Tuesday that it did not accept accusations from Google Inc that the Chinese government was making it difficult for Gmail users to use the service in the country.
This is an unacceptable accusation, Foreign Ministry spokeswoman Jiang Yu told a regular news conference, without elaborating.
On Monday, a Google spokeswoman said any difficulty users in China may have faced in recent weeks accessing Google's email service was likely the result of government blocks.
Gmail users in China said they were still able to log in to their accounts, but were unable to perform tasks such as sending email and accessing their address books.
On Monday, Google shares were up 2.8 percent, while Chinese rival Sina Corp rose 5.5 percent and Chinese search engine operator Baidu Inc rose 2.9 percent.
Google's run-ins with the Chinese government began in January 2010, when the company said it was no longer willing to censor search results in the country. Previously, the company included a disclaimer on its China service that searches may not be complete because of local laws.
Searches for terms deemed sensitive by Chinese censors are routinely blocked. Chinese search engines such as that offered by Baidu already voluntarily filter searches.
This is not the first time Google has accused China of interfering with its services. In January, Google said it had uncovered sophisticated China-based attacks on human rights activists using its Gmail service around the world.
The months-long censorship dispute that Google had with the Chinese government was a diplomatic flashpoint in Sino-U.S. relations in 2010.
Censorship of Web content has intensified in China following calls on foreign websites for a Jasmine Revolution, which are anti-government gatherings inspired by demonstrations in the Middle East and North Africa.
(Writing by Ben Blanchard and Lee Chyen Yee; editing by Chris Lewis)