The Guardian reports: Any attempt by the US to extradite the NSA whistleblower Edward Snowden from Hong Kong for espionage could take years and be blocked by China, legal experts have said.

The warning comes after it emerged on Friday that the US has charged Snowden with theft of government property, unauthorised communication of national defence information and wilful communication of classified communications intelligence to an unauthorised person. The latter two charges are part of the US Espionage Act.

Legislators in Hong Kong responded by calling for mainland China to intervene in the case. Snowden, 29, who is reportedly in hiding in Hong Kong, was last seen on 10 June. He is understood to have made contact with human rights lawyers in anticipation of a legal action from the US.

The US and Hong Kong have had an extradition treaty since 1998, a year after Hong Kong was transferred from British to Chinese rule. Scores of Americans have been sent back for trial under the treaty.

While espionage and theft of state secrets are not cited specifically in the treaty, equivalent charges could be pressed against Snowden under Hong Kong’s official secrets ordinance, legal experts said.

The timeframe for such proceedings remains unclear, but Hectar Pun, a barrister with human rights expertise, said such an extradition could take three to five years.