"Just now... WikiLeaks began publishing the Syria files, more than two million emails from Syrian political figures, ministries and associated companies dating from August 2006 to March 2012," said Sarah Harrison, spokeswoman for the anti-secrecy website.
The latest disclosures could throw fresh light on the workings of the Syrian regime and its interactions with allies in the run-up to and during the current bloody crackdown.
The British-based Syrian Observatory for Human Rights says the 16 months of bloodshed in Syria have claimed more than 16,500 lives.
WikiLeaks founder Julian Assange, who is currently holed up in Ecuador's embassy in London seeking political asylum, said in a written statement: "The material is embarrassing to Syria, but it is also embarrassing to Syria's external opponents.
"It helps us not merely to criticise one group or another, but to understand their interests, actions and thoughts.
"It is only through understanding this conflict that we can hope to resolve it."
WikiLeaks said the first files, released on Wednesday, reveal that Italian defence giant Finmeccanica has provided communications equipment to the Syrian regime since the unrest began.
The communications system was provided by Finmeccanica's subsidiary SELEX Elsag, in claims by WikiLeaks published by Italian magazine L'Espresso.
WikiLeaks' announcement comes a day after Russia denied having discussed with Washington offering exile to Syria's President Bashar al-Assad.
It also comes ahead of a meeting Friday in Paris of the "Friends of Syria" group of countries which support tougher action against Assad's government.
WikiLeaks said the 2,434,899 emails came from Syrian ministries including foreign affairs, finance and presidential affairs. There are around 400,000 emails in Arabic but also 68,000 in Russian.
Harrison said WikiLeaks could not comment on the full contents of the release, which is being organised in collaboration with media partners in countries including the US, Lebanon, Egypt, Germany, France, Italy and Spain.
"This is a large data set. It will take time for these stories to come out," she said at a press conference in London announcing the release.
She refused to comment on how WikiLeaks had obtained the emails, telling AFP: "We never comment on our sourcing."
The publication comes amid continued wrangling between world powers about how the bloody conflict in Syria should be tackled.
Russia has indicated it will stay away from the Paris meeting on Friday after accusing the West of seeking to distort a deal struck last weekend for a political transition in the violence-hit nation.
Moscow's move to shun the gathering comes after UN-Arab League peace envoy Kofi Annan stressed that a ceasefire was imperative.
Assange, meanwhile, has been inside the Ecuadorian embassy since June 19 in a bid to avoid extradition to Sweden, where he is wanted for questioning over allegations that he sexually assaulted two female former WikiLeaks volunteers.
Assange denies the allegations, which he says are politically motivated. The 40-year-old Australian fears he could be extradited from Sweden to the United States, where he claims he could face the death penalty.
WikiLeaks enraged Washington in 2010 by publishing a flood of secret documents about the wars in Iraq and Afghanistan, as well as more than 250,000 confidential US diplomatic cables that embarrassed a slew of governments.
The Syria files are WikiLeaks' first major publication since it began disclosing internal emails from the US-based intelligence firm Stratfor in February.