Image caption The bloggers have been hailed for stopping negative online rumours

Vietnamese propaganda officials have admitted deploying people to engage in online discussions and post comments supporting the Communist Party's policies.

The party has also confirmed that it operates a network of nearly 1,000 "public opinion shapers".

They are assigned with the task of spreading the party line.

The tactic is similar to China's model of internet moderators who aim to control news and manipulate opinion.

'Political opportunists'

Hanoi Propaganda and Education Department head Ho Quang Loi said that the authorities had hired hundreds of so-called "internet polemists" in the fight against "online hostile forces".

While the exact number of these activists is unknown, Mr Loi revealed that his organisation is running at least 400 online accounts and 20 microblogs.

Regular visitors on popular social media networks in Vietnam such as Facebook have long noticed the existence of a number of pro-regime bloggers, who frequently post comments and articles supportive of the Communist Party.

The bloggers also take part in online discussions, where they fiercely attack anybody who they see as critical of the regime.

On a recent BBC Vietnamese Facebook wall - linked to a story about measures to clamp down on dissent - one such blogger asked why it was that the US "gave themselves the right to criticise other nations on human rights".

"They should have a look at their own record!" the blogger stated.

Another post criticises pro-democracy campaigners.

"The so-called democracy activists and intellectuals are becoming more and more ridiculous. They have shown their true colour as political opportunists. Their despicability has no bounds," it says.

Mr Loi said such bloggers helped a great deal in stopping negative rumours and had blocked online calls for mass gatherings in the city.

Vietnam's capital saw at least dozen public protests in 2011, but the number was greatly reduced last year.

The authorities also employ a force of 900 "public opinion shapers" who help talk up government policies and promote the party line across the country.

It is not clear whether these operatives, and the bloggers, are on official payrolls.

But they are being praised by officials as a sophisticated and effective tool in controlling public opinion.