And he left with the help of WikiLeaks, who assisted with Snowden's "political asylum in a democratic country, travel papers (and) safe exit from Hong Kong." the group said on Twitter.
Snowden took off not long after the United States asked Hong Kong to extradite the man who leaked top-secret details about U.S. surveillance programs.
The U.S. government had also asked Hong Kong to issue a provisional arrest warrant for Snowden, a former contractor for the National Security Agency, the Hong Kong Special Administrative Region (HKSAR) said.
But officials said there were problems with the request.
"Since the documents provided by the U.S. government did not fully comply with the legal requirements under Hong Kong law, the HKSAR government has requested the U.S. government to provide additional information," the Hong Kong government said in a statement. "... As the HKSAR government has yet to have sufficient information to process the request for provisional warrant of arrest, there is no legal basis to restrict Mr. Snowden from leaving Hong Kong."
The statement did not say what additional information Hong Kong needed from the United States, nor did it say where Snowden was headed.
U.S. federal prosecutors have charged Snowden with theft of government property, unauthorized communication of national defense information, and willful communication of classified communications intelligence to an unauthorized person.
The latter two allegations amount to espionage under the federal Espionage Act.
News of Snowden's departure followed a day of intense speculation over whether Hong Kong would extradite Snowden to the United States.
Hong Kong Executive Council member Regina Ip said authorities could arrest Snowden if his actions qualify as criminal under Hong Kong law, China's state-run Xinhua news agency reported earlier Sunday. The executive council decides on policy matters for Hong Kong, a special administrative region of China.
But if the charges against him are deemed to be political in nature, the 30-year-old would not be extradited, Ip told Xinhua.
How the case unfolded
Snowden has admitted in interviews he was the source behind the leaking of classified documents about the NSA's surveillance programs. Those leaks were the basis of reports in Britain's Guardian newspaper and The Washington Post this month. The Guardian revealed Snowden's identify at his request.
The documents revealed the existence of the programs that collect records of domestic telephone calls in the United States and monitor the Internet activity of overseas residents.
The revelation of the leaks rocked the Obama administration and U.S. intelligence community, raising questions about secret operations of the NSA and whether the agency was infringing on American civil liberties.
Obama, top legislators and national security officials defend the surveillance programs as necessary to combat terrorism and argue that some privacy must be sacrificed in a balanced approach.
They say the law allows collection of metadata, such as the time and numbers of phone calls, and that a special federal court must approve accessing the content -- listening to the call itself.
In interviews this month, Snowden said he fled with the classified documents after taking a leave of absence from his job as an intelligence analyst for NSA contractor Booz Allen Hamiliton. The company has since fired him.
A series of blog posts this week purportedly by Snowden said he leaked classified details about U.S. surveillance programs because President Barack Obama worsened "abusive" practices, instead of curtailing them as he promised as a candidate.
Snowden said that he had to get out of the United States before the leaks were published by the Guardian and The Washington Post to avoid being targeted by the government.
In an interview published Sunday, Snowden told the South China Morning Post that the U.S. government is hacking Chinese mobile phone companies to steal millions of text messages. The Guardian also reported Snowden's latest claims.
Snowden had earlier told the Post that U.S. intelligence agents have been hacking computer networks around the world, including in China, for years.
Hong Kong has requested clarification from the United States on such reports. The HKSAR said it will continue to follow up on the matter so as to protect the legal rights of the people of Hong Kong.