Cambodia’s national assembly has passed a state of emergency law granting the country’s autocratic leader, Hun Sen, vast new powers, in what rights groups say is a cynical move to exploit the coronavirus pandemic.

The legislation, passed on Friday, is expected to further weaken democratic rights in a country that has no functioning opposition and where key political opponents are either in prison or exile.

While human rights experts agreed some restrictions were needed to slow the spread of coronavirus, it is feared that many leaders are using the emergency to grab power.

In Cambodia, the new legislation contains sweeping provisions allowing the government to carry out unlimited surveillance of telecommunications and to control the press and social media. The government would also gain the ability to restrict freedom of movement and assembly, seize private property and enforce quarantines.

In addition, a catch-all clause would authorise “other measures that are deemed appropriate and necessary in response to the state of emergency”.

Hun Sen initially downplayed the threat of coronavirus, and at one point threatened to throw journalists out of press conferences if they wore masks. When the Westerdam cruise ship was turned away by several other countries concerned about the outbreak, Hun Sen not only allowed the ship to dock but attracted international attention by hugging passengers as they disembarked.

The country, where a lack of media freedom means scrutiny is limited, has since recorded 115 cases of the virus. Schools and entertainment venues have been shut, and wider travel restrictions announced.

The state of emergency could be invoked whenever the country is considered to be facing a great risk, such as in a pandemic, war or disruption to public order, according to the law.

Anyone found guilty of disobeying emergency measures, which are vaguely worded and could be used to target government critics, faces 10 years in prison.

David Griffiths, director of the office of the secretary-general at Amnesty International, described the legislation as indefensible.

“This is a blatant exploitation of public panic around Covid-19 and threatens to eviscerate the human rights protections which are guaranteed by the Cambodian constitution and international human rights law,” he said.

Independent journalists, government critics and people speaking about Covid-19 online are being arrested on a daily basis, he added.

This week, Sovann Rithy, a journalist working for broadcaster TVFB, was arrested for quoting a recent speech by Hun Sen in which the prime minister said: “If motorbike-taxi drivers go bankrupt, sell your motorbikes for spending money. The government does not have the ability to help.” The police arrested Rithy, stating that Hun Sen’s words were intended as a joke.

Griffiths said: “The idea of concentrating even more unchecked power into the hands of this government is worrying in the extreme.”

Asean Parliamentarians for Human Rights (APHR), an association of members of parliament from south-east Asian countries, said similar laws are being used across the region to crack down on critics.

This includes the Philippines, where individuals can be jailed for spreading false information about Covid-19, and Thailand, where an emergency decree allows the prime minister to censor publications for a broad range of reasons. Officials in Thailand also have additional powers to arrest and hold people without charge if they are suspected of having a role in causing an emergency.

Thailand’s prime minister, Prayut Chan-o-cha, and Hun Sen, “have both shown in the past already creative ways to hang on to power”, said Teddy Baguilat, a former Philippines MP and board member of APHR. “We need to make sure that the Covid-19 pandemic does not become their new tool to further legitimise and secure their authoritarian leadership.”