BEIJING - The Cyberspace Administration of China (CAC) on Thursday dismissed allegations that Chinese authorities had hacked into Microsoft Corp's Outlook email service as "groundless slander".

CAC spokesman Jiang Jun made the remarks in response to media inquiries after the China-based web monitoring group Greatfire.org claimed that Chinese Outlook users were victims of a "man-in-the-middle" (MITM) hacking attack.

The accusation aimed to "incite dissatisfaction and smear China's cyberspace management system," Jiang said.

Jiang brushed aside the claim as "unsupported speculation, a pure slanderous act by overseas anti-China forces," while describing Greatfire.org as being run by foreign anti-China organizations.

The Chinese government is a staunch advocate for cyber security and stands firmly against any sort of cyber attack, he said, adding that China will crack down on online offensive maneuvers initiated in China and those launched via Chinese Internet infrastructure in line with law.