China Mobile has issued an apology after nearly half of China's cell phone users were sent unwanted junk text messages this week.

According to media reports, China Mobile blamed management loopholes that allowed seven online advertising firms, reportedly including Focus Media, to send unsolicited SMS messages yesterday to over 200 million users.

"This was an SMS spam tidal wave. When the mobile phones of 200 million people in China all bleeped at once to tell them they had a new SMS spam, the authorities had to sit up and listen," said Graham Cluley, senior technology consultant for Sophos. "Misguided companies may be tempted to exploit modern technology in their attempt to get marketing messages in front of their potential audience, but spamming cell phones is simply not acceptable. China would be wise to follow other countries around the world and clarify the rules regarding spam SMS messages."

China is believed to have some 555 million cell phone subscribers, and personal information is frequently traded between different companies who wish to target potential customers.