But he said he "could not ignore the alleged network invasion and unfair comments" by the US.

Leung said: "Snowden has left, but the matter is not over. The Hong Kong government needs to safeguard the interests of Hong Kong.

"A few days ago, the government wrote to the US side officially asking for a full explanation on whether it had hacked Hong Kong's networks and invaded Hong Kong citizens' privacy, as claimed by Mr Snowden. But we have received no response so far."

Meanwhile, Secretary for Justice Rimsky Yuen Kwok-keung issued a rebuttal of US claims that Hong Kong deliberately stalled over Washington's request for Snowden to be detained under a provisional arrest warrant.

"I can tell you in no uncertain terms that we have not been deliberately delaying," Yuen said.

White House spokesman Jay Carney had earlier said Washington did not believe the explanation that it was a "technical" decision by Hong Kong immigration authorities. "We do not buy the suggestion that China could not have taken action," he said.

In a detailed response, Yuen outlined a series of "substantive" shortcomings in the information provided by Washington to support its request that Snowden be detained.

Meanwhile, in a front-page commentary in the overseas edition of , Beijing praised former CIA analyst Snowden, describing him as young idealist whose actions had served to "tear off Washington's sanctimonious mask".

Experts said it was unlikely that Washington would retaliate in tangible terms and the dispute would remain a war of words.

China yesterday refuted a US accusation that it had facilitated Snowden's departure from Hong Kong, after Washington said Beijing had chosen to release him.

"It is unreasonable for the US to question Hong Kong's handling of affairs in accordance with the law, and the accusation against the Chinese central government is groundless," Foreign Ministry spokeswoman Hua Chunying told a regular press briefing in Beijing.

She added: "China cannot accept that."

But analysts said neither side would be keen to let ties deteriorate just weeks after a successful summit between Barack Obama and President Xi Jinping .

"China does not want this to affect the overall situation. Beijing has always maintained a relatively restrained attitude because Sino-US relations are all important," said Zhao Kejing, a professor of international relations at Tsinghua University.

"The US has no real reason to take substantial action or exert greater pressure either," he said.

Professor Simon Shen Xu-hui, of the Social Science Faculty of the Chinese University, said Beijing had been "reserved" in its comments and Washington's criticism had not been particularly harsh. He commented: "It's just saying what it has to say."

He said it was unlikely the process of including Hong Kong into the US list of visa-free destinations would be affected. He added: "It's more about attracting foreign investment to the US, so it's quite unrelated in this matter."

Stanley Lau Chin-ho, vice-chairman of the Federation of Hong Kong Industries, said he did not believe the US would retaliate against Hong Kong.

Exports to the US account for about 20 to 30 per cent of annual export revenue, he said, adding: "If the United States … imposed sanctions on Hong Kong, then its own companies would be impacted too."

Lau said the possible visa-free status was not especially important to the business sectors.

He said: "All along, we have to apply for a visa to travel to the US. It will be more convenient if we don't have to, but we are used to it already anyway."

Travel Industry Council chief Joseph Tung Yao-chung also said travellers to the US accounted for only a small percentage.