"He goes to the very countries that have, at best, very tense relationships with the United States," said Rep. Ileana Ros-Lehtinen (R., Fla.), adding that she feared Snowden would trade more U.S. secrets for asylum. "This is not going to play out well for the national security interests of the United States."
Snowden helped the Guardian of London and the Washington Post disclose U.S. surveillance programs that collect vast amounts of phone records and online data in the name of foreign intelligence but often sweep up information on American citizens.
Snowden had been in hiding for several weeks in Hong Kong, a former British colony with a degree of autonomy from China. The United States formally sought Snowden's extradition from Hong Kong but was rebuffed; Hong Kong officials said the request did not fully comply with their laws.
The Justice Department rejected that assertion, saying its request met all requirements of the extradition treaty between the United States and Hong Kong.
Sen. Dianne Feinstein (D., Calif.), chairwoman of the Senate intelligence committee, said she believed China played a role in allowing Snowden to leave and said Beijing had wasted an opportunity to improve relations with the United States.
"China clearly had a role in this, in my view. I don't think this was just Hong Kong without Chinese acquiescence," Feinstein said on CBS's Face the Nation.
The Ministry of Foreign Affairs in Beijing said in a statement Sunday evening it had seen the reports of Snowden's departure but did not have "specific details."
Ken Lieberthal, a China expert with the Brookings Institution, said it was doubtful Beijing - or Hong Kong - had much appetite for having Snowden within their borders.
"I think the Chinese government's position has been 'We don't want to have anything to do with this,' " he said.
A State Department official said the United States was in touch through diplomatic and law enforcement channels with countries that Snowden could travel through or to, reminding them that Snowden was wanted on criminal charges.
The White House would say only that President Obama had been briefed by his national security advisers.
Russia's state ITAR-Tass news agency and Interfax cited an unnamed Aeroflot airline official as saying Snowden was on the plane that landed Sunday afternoon in Moscow.
Upon his arrival, Snowden did not leave Moscow's Sheremetyevo Airport. One explanation could be that he was not allowed; a U.S. official said Snowden's passport had been revoked, and special permission from Russian authorities would have been needed.
The Russian media report said Snowden intended to fly to Cuba on Monday and then on to Caracas, Venezuela.
With each suspected flight, efforts to secure Snowden's return to the United States appeared more complicated. The United States does not have an extradition treaty with Russia but does with Cuba, Venezuela, and Ecuador. Even with an extradition agreement, though, any country could give Snowden a political exemption.
It also was not clear Snowden was finished with disclosing highly classified information.
Feinstein said she had been told he had perhaps more than 200 sensitive documents.
This article contains information from the Washington Post.