Media organisations in Nigeria have expressed alarm as the government prepares to follow its controversial ban on Twitter with wider regulations reining in the press and social media companies.

A new amendment proposed by lawmakers in President Muhammadu Buhari’s All Progressive Congress party would allow the government to determine a code of conduct for Nigerian media agencies and journalists, who could be liable to be fined and prosecuted for “fake news” and other breaches of the code.

Media organisations have branded the amendment and other proposed moves to clamp down on social media companies in recent weeks as an “attack on free speech”. It follows a ban on Twitter in early June that sparked a series of curbs. For years, Nigerian authorities had promised a crackdown on social media platforms, as disruptive protest movements used them to organise, despite government attempts to suppress them.

“It is deeply disturbing and is causing a lot of concern for us who work in the media,” said Stephanie Adams, a programme officer of media freedoms at the Premium Times Centre for Investigative Journalism, one of a number of organisations to criticise the proposals by lawmakers. The amendment, which is yet to be voted on, would give the government the power to appoint the majority of members of the Nigerian Press Council, a body overseeing the media, and determine a legally binding code, she said.

“It’s an attack on the independence of the media. The board should be a composition from various media and other relevant stakeholders,” she said. “Not appointed by the federal government or the minister of information. There should be some form of autonomy.”

Journalists could face fines and be imprisoned for three years under the proposed amendment to the Nigerian Press Council Act. Nigeria’s officials have also said social media networks must soon register with Nigerian regulators and have offices in the country.

Fears of a growing hostility to critics and opposition groups are mounting in Nigeria – as many in the country lament multiple crises of rising insecurity, a suffering economy and an attack on freedoms.

In early June, the government ordered telecommunications networks to block the use of Twitter after the social media company deleted a controversial tweet by President Buhari for violating its terms of use. Buhari had threatened pro-Biafra groups – accused of attacks on police and civil authorities – by referencing his role as a brigade major during the bitter 1967 Biafra war.

Facebook also deleted the post on its site, yet has so far avoided direct criticism from the government. Only a fraction of an estimated 40 million Twitter users in the country have been able to bypass the ban, via virtual private networks whose use has rapidly increased.

The removal of Buhari’s tweet fuelled a wave of angry recriminations by government officials, some of whom have since joined the Indian social media app Koo. Yet concerns about Twitter had been raised by officials for several months.

A lack of action by Twitter on deleting inciting posts has been a sore point. More significantly, the government objected to the use of Twitter to organise mass EndSars protests against police brutality, which erupted in Nigeria last October.

Sars refers to the since-disbanded, infamously brutal Special Anti-Robbery Squad.

The strength of the demonstrations set authorities on a collision course with Twitter, said Adewunmi Emoruwa, the founder of Gatefield, a public policy organisation that was targeted by authorities for supporting the protests.

“EndSars was clearly the tipping point for the Buhari administration, which saw the protests as an attempt at regime change. Not only was the platform the key vehicle for organising by citizens, the visible involvement of Twitter’s founder Jack [Dorsey] in mobilising support for the anti-police brutality protesters created hostility towards the company from the administration,” he said.

Nigeria’s information minister, Lai Mohammed, has in recent weeks ramped up fierce criticisms of Twitter and its CEO, Jack Dorsey. In October, Dorsey retweeted calls to raise money for protesters in bitcoin, after the Nigerian central bank suspended the bank accounts of groups supporting the protests.

Mohammed has accused Twitter’s operations of being “suspicious” and accused Dorsey of being responsible for lives lost and property damaged during the demonstrations.

“If you ask people to donate money via bitcoin for EndSars protesters, then you are vicariously liable for whatever the outcome of the protest,” Mohammed said last week. “We have forgotten EndSars led to loss of lives, including 37 policemen, six soldiers, 57 civilians, while property worth billions of naira were destroyed,” he added.

Dorsey has in turn posted numerous tweets of the Nigerian flag, as protesters defied police orders against organising earlier this month, and promoting bitcoin in Nigeria, which is restricted.

In the weeks since the ban, moves by the government have sparked growing alarm. Nigeria’s attorney general ordered prosecutors to pursue anyone violating the Twitter ban. A court ruling this week by the West African regional bloc Ecowas barred the Nigerian government from prosecuting individuals and corporate bodies.

The government has begun dialogue with Twitter, increasing the likelihood the ban will be reversed, yet many fear the moves to regulate social media and Nigerian news organisations could have a lasting effect.