Google shares were marginally down Wednesday morning on the Nasdaq.

Beijing - Google services were once again being disrupted in China on Friday after a brief respite on Thursday, users and an anti-censorship group reported, continuing more than a month of severe disruption.

Features such as Google's search, maps, online advertising services and e-mail client have been rendered almost inaccessible for users in China.

The Google disruption began in the run-up to the 25th anniversary of the government's bloody crackdown on pro-democracy demonstrators around Beijing's Tiananmen Square.

China maintains tight control over the Internet, nipping in the bud any signs of dissent or challenges to the ruling Communist Party's leadership.

Google declined to comment.

China-based anti-censorship group reported that Google services appeared once again to be inaccessible within China.

The “Great Firewall”, the tool the Communist Party uses to block websites it deems undesirable, experienced a glitch that allowed Google services to work, said.

“It looks like merely a bug of the Great Firewall,” said a member of the group who used a pseudonym. “It's blocked again.”

The brief restoration of access had occurred as US Secretary of State John Kerry was visiting Beijing, where cyber-security was high on the list of topics he discussed.

Other online services are also experiencing disruption in China, which began last week. These include South Korean Naver's Line and KakaoTalk, owned by South Korea's Kakao, both of which are mobile messaging apps.

Disruptions have also been affecting Yahoo's photo-sharing site, Flickr, and Microsoft's OneDrive cloud storage platform.

Other overseas online services, such as social networks Facebook and Twitter, and Google-owned video site YouTube, have been blocked in China for years. - Reuters