Google said Monday the Chinese government is interfering with its email services in China, making it difficult for users to access its Gmail program, amid an intensified internet crackdown following widespread unrest in the Middle East.

"There is no technical issue on our side; we have checked extensively. This is a government blockage carefully designed to look like the problem is with Gmail," the company said in a brief statement.

China has some of the world's strictest internet controls and blocks many popular social media sites, including YouTube, Facebook and Twitter. The government intensified those efforts after pro-democracy protest erupted across the Middle East in January.

Around that time, anonymous calls for protesters to gather for a "Jasmine Revolution" in China triggered a crackdown by Chinese authorities, who stepped up web censorship and deployed huge numbers of police to planned protest sites. No protests happened.

A Google spokesperson said users in China, the world's most populous internet market, have reported having intermittent problems with the service since the end of January.

Problems include difficulty accessing the home page for Gmail and problems sending emails when logged into the service. The instant messaging function is often not working as well.

Google officials said the blocking appears to be more sophisticated than other problems experienced by users in the past because the disruption is not a complete block.

In addition, a March 11 blog post by Google about security said the company had "noticed some highly targetted and apparently politically motivated attacks against our users. We believe activists may have been a specific target." In the posting, Google declined to elaborate on which activists had been targetted or where the attacks had come from.

A company spokesperson refused to say if Google has raised the issue directly with Chinese government officials.

China's Foreign Ministry had no immediate comments on Google's accusation.

Google has had highly public run-ins with the Chinese government.

In January last year, Google announced that it would no longer co-operate with the government's requirement to censor search results for banned sites. It also complained about major attacks on its website by Chinese hackers, suggesting the government may have instigated the attacks.

Attacks were also mounted against email accounts by activists working on human rights in China at that time.

Google moved its Chinese-language search engine to Hong Kong, which operates under separate rules from the rest of mainland China.