By Cris Chinaka

HARARE (Reuters) - Zimbabwe's government has blocked mass SMS bursts ahead of next week's election, hobbling a powerful source of non-official information in the tightly controlled southern African state, activists and a phone company source said on Friday.

With the clock ticking to the July 31 poll in which President Robert Mugabe is looking to add to his 33 years in power, web portal Kubatana.net said it had noticed this week that its mass text messages were mysteriously getting lost.

Its provider, Econet Wireless - Zimbabwe's largest mobile phone firm with 8 million subscribers out of a population of 13 million - declined to comment.

However, a senior company source confirmed the firm had bowed to government pressure to block mass SMS services around the election "in the interest of peace, national security and stability".

"We have just been told we cannot be facilitating bulk SMSs during the elections, roughly for the next two or so weeks," the source said. "Our understanding is that they will take our network down or cancel our license if there is any violation."

A spokeswoman for the regulator, part of the telecoms ministry, declined to comment.

Although Internet penetration rates have soared since the end of a long economic meltdown in 2008, many Zimbabweans only have simple phone handsets, making the plain old SMS a more effective way to disseminate news and views to a mass audience.

Kubatana, whose messages contained headlines, quotations, proverbs and political questions, said the shutdown was an infringement of the freedom of expression enshrined in a constitution only ratified in May.

"Kubatana.net views the interference in our work as obstructive, repressive and hostile," it said in a statement.

ONLINE FREEDOM

With Africa's oldest leader in no mood to ride off into the political sunset, there are likely to be more disputes over control of technology and the Internet, the breeding ground of people-power uprisings against oppressive governments in the Middle East and North Africa.

Faced with a daily diet of pro-Mugabe propaganda in newspapers controlled by his ZANU-PF party and on state television and radio, many Zimbabweans have turned to cyberspace for an alternative view.

Top of the list is purported ZANU-PF "Deep Throat" Baba Jukwa, whose Facebook page has attracted nearly 300,000 followers of his salacious tales of scandal and intrigue at the heart of the ruling party.

Internet giant Google has lent its weight, launching a 'Zimbabwe election hub' (www.google.co.zw/elections/ed/zw) to bring all stories and issues under one web address.

Fearing a rigged vote or result skewed by threats or violence - as happened in the last election in 2008 - Zimbabweans have also set up sites to monitor the progress of the election and conduct of security forces.

Prominent among these is votewatch263.org, a 'crowd-sourcing' website that lets people report incidents - positive or negative - that are then plotted on an interactive map, a concept first used in Kenya after violent elections in 2007.

"News and information is circulating faster now than at any other time. We don't need to listen to the ZBC bulletins or rely on a copy of the Daily News to know what's going on," said votewatch263 spokeswoman Koliwe Nyoni Majama.

Even though the atmosphere on the ground has been relatively peaceful compared with 2008, online tensions are high.

Hackers took out the website of the Zimbabwe Ministry of Defense last month and the SMS blockade suggests Mugabe's cyber-police - believed to be trained by China and Russia - will be keeping a close eye on sites such as votewatch263.

The prospects of retaliation are especially high since, as recipients of foreign donor funding, they are open to accusations of being a front for hostile Western governments, a common Mugabe refrain.

"The people who set up the software put some security settings in place," Majama said. "We've tried our level best to get it on for as long as possible - but everything is possible."

(Additional reporting and writing by Ed Cropley; Editing by David Evans)