Cambodia has seen a rapid increase in internet use in recent years, and Premier Hun Sen's government -- which dissolved the main opposition party in 2017 - has intensified a crackdown on online dissent.

A government spokesman dismissed concerns over the gateway (NIG), a system which will funnel all international internet connections through a single entry point, saying it would prevent online crime and promote "national interests".

But Phay Siphan also told AFP the authorities "will destroy those (internet) users who want to create rebellion" against the government.

A sub-decree signed by Hun Sen and obtained by AFP on Wednesday stated that the NIG would control web connections in order to enhance "national revenue collection, to protect national security and preserve social order".

It instructed the gateway's operator to work with Cambodian authorities "to take actions in blocking and disconnecting any network connections" that were deemed to contravene these goals, or to violate "morality, culture, traditions and customs".

The operator will be required to submit reports about internet traffic regularly to authorities.

Chak Sopheap, executive director of the Cambodian Centre for Human Rights, said the NIG would facilitate mass surveillance, through the interception and censorship of digital communications and the collection of personal data.

"The establishment of the NIG is of grave concern for the future of fundamental human rights in Cambodia," she said, adding that "it will become another instrument for the Royal Government of Cambodia to control and monitor the flow of information in Cambodia".

Ith Sothoeuth, director of the Cambodian Center for Independent Media, said the vague language in the document bestowed the power to block comments critical of the government.

"It's worrisome," he said.

Comparisons have been drawn to China's "Great Firewall", which deploys a vast and sophisticated surveillance state to scrub the internet of dissent, and prevents citizens from accessing international social networking sites such as Facebook and Twitter.

Internet subscriptions in Cambodia have soared over the last decade, from 5 million in 2014 to 20.3 million last year, according to government statistics.

Facebook is the most popular social media platform in Cambodia with nearly 11 million users.

Hun Sen is one of the world's longest-serving leaders, maintaining a 36-year grip on power with methods that critics say include jailing political opponents and activists.