Hundreds of people have marched to the US consulate in support of Edward Snowden, an American citizen who leaked top-secret information about US surveillance programs.

Mr Snowden, who worked as a contract employee at the National Security Agency, revealed to The Guardian newspaper the existence of secret surveillance programs that gathered Americans' phone records and other data.

He is believed to be in Hong Kong.

The 29-year-old American has yet to be publicly charged with any crime and no known warrants have been issued for his arrest.

Protesters braved the rain and marched to the US Consulate in Hong Kong to show their support.

Some held placards reading "Betray Snowden. Betray Freedom" as they walked.

They also chanted pro-Snowden slogans when they gathered at the rear of the US Consulate.

In an interview with the South China Morning Post, Hong Kong's main English-language newspaper on Wednesday, Snowden alleged that the US National Security Agency hacked 61,000 targets, including hundreds in Hong Kong and mainland China.

Facebook reveal data agreement

Meanwhile, it emerged today that Facebook and Microsoft have struck agreements with the US government to release limited information about the number of surveillance requests they receive.

It is a modest victory for the companies as they struggle with the fallout from disclosures about a secret US government data-collection programme.

Facebook became the first to release aggregate numbers of requests, saying in a blog post that it received between 9,000 and 10,000 US requests for user data in the second half of 2012, covering 18,000 to 19,000 of its users' accounts.

Facebook has more than 1.1 billion users worldwide.

It is believed that the majority of those requests are routine police inquiries.

However, under the terms of the deal with the US Justice Department, Facebook is precluded from saying how many were secret orders issued under the Foreign Intelligence Surveillance Act.

Until now, all information about requests under FISA, including their existence, were deemed secret.

Microsoft said it had received requests of all types for information on about 31,000 consumer accounts in the second half of 2012.