WikiLeaks founder Julian Assange vowed to keep exposing secret documents and defended his controversial website, two years after it published a massive trove of sensitive US diplomatic cables.

Marking the anniversary of "cablegate," Assange alleged in a commentary published Thursday that his self-styled anti-secrecy website had uncovered US attempts to hide atrocities, coerce other governments and dominate the global economy.

"Since 2010, Western governments have tried to portray WikiLeaks as a terrorist organization, enabling a disproportionate response from both political figures and private institutions," he wrote in the Huffington Post.

"It is the case that WikiLeaks' publications can and have changed the world, but that change has clearly been for the better," he said, citing some of the once secret State Department cables that his site disclosed.

"Two years on, no claim of individual harm has been presented, and the examples (cables) above clearly show precisely who has blood on their hands."

By exposing details of the deaths of Iraqi civilians and the corruption of the Tunisian regime, WikiLeaks had helped force the US military's withdrawal from Iraq in 2011 and had fueled an uprising in Tunisia that spread across Arab countries, according to Assange.

Despite condemnation by the US government, the Australian ex-hacker said his organization would not shy away from divulging more secret documents and would combat attempts to block supporters from making online financial contributions to WikiLeaks.

"We will continue our fight against the financial blockade, and we will continue to publish."

He said the leak of the diplomatic cables had confirmed press reports that the US was carrying out a covert bombing campaign against militants in Pakistan as well as drone strikes in Yemen, with the government there hiding the US role.

Assange's commentary appeared as the army private accused of leaking the US documents to WikiLeaks, Bradley Manning, testified for the first time at a pre-trial hearing after two years in detention.

Assange has been holed up in Ecuador's London embassy for five months to avoid extradition to Sweden, where he is facing allegations of rape and sexual assault, charges he strongly denies.

He says that if extradited, he could be handed over to the United States for prosecution.

Assange was arrested in 2010 after WikiLeaks enraged Washington earlier that year by leaking hundreds of thousands of classified US documents on the wars in Iraq and Afghanistan, as well as embarrassing diplomatic cables from US embassies around the world.