At first, a social media campaign calling on Sudanese people to participate in a stay-at-home strike seemed doomed to fail: only a quarter of the population have access to the internet. And looking back at Sudan’s history, political mobilisation had occurred through unions, not social media. But, somehow, it worked.

On 27 November, the capital awoke to half-empty streets as many businesses and schools in Khartoum remained closed. Another stay-at-home strike, coupled with a boycott of government transactions, followed on 19 December. By then, what had begun as a protest against subsidy cuts had morphed into a movement advocating for broader change.

Members of the ruling party denied widespread participation in the civil disobedience campaign. But in a sign of growing unease, President Omar al-Bashir challenged the activists “to come out on to the streets”, vowing that “this regime will not be overthrown by keyboards”. The government didn’t respond to the Guardian’s repeated requests for comment.

The civil disobedience campaign is the biggest show of public dissent since September 2013, when security forces crushed street protests that some thought would force Bashir, who took power in a 1989 military coup, to step down.

“People went to the street, they protested – and they were killed,” said one young activist who helped to organise the demonstrations as part of a movement called Sudan Change Now. “But the regime did not fall. To me, it was a shock,” added the activist, who didn’t want to be named for fear of being targeted.

According to rights groups, 200 people died when security forces opened fire on demonstrators (the government put the death toll at around 80), while hundreds of dissidents were reportedly arrested.

With fear of a repeat of the 2013 violence still hanging over the capital, activists say the non-confrontational nature of the campaign was key in drawing widespread support.

“You will not be arrested for posting on social media,” said Amna Osman, 23, a psychology student and one of many political activists who quickly latched on to the social media campaign. Osman was among those detained in September 2013.

The call for civil disobedience came just weeks after the official conclusion of a government-led national dialogue, highlighting public disenchantment with a process that promised far-reaching reforms in the aftermath of the 2013 protests, but failed to bring about genuine change.

A final document summarising the outcome of the dialogue, produced in October and seen by the Guardian, outlined a series of recommendations and constitutional amendments to be implemented by a new government that incorporates other parties.

But even as the ruling National Congress Party (NCP) declared the successful completion of the dialogue, security forces continued to tighten their grip on the media and the opposition.

More than 20 members of the Sudanese Congress party were arrested in November. The same month, at least four independent newspapers had one or more of their editions confiscated, while the independent Al-Tayar newspaper was shut down for three days in December.

Most of Sudan’s major opposition parties boycotted the dialogue, claiming the ruling party wasn’t willing to make genuine concessions, such as curtailing the power of the presidency and the sprawling national security apparatus.

“What we are getting is more of the same,” said Ghazi Salahuddin Atabani, who leads the Reform Now Movement, an opposition party that has been part of the national dialogue. “We will see the same bloated kind of government, intended not to deliver goods to the people, but to incorporate as many parties as possible under the wing of the NCP.” He said every request by his party to hold a political rally had been denied in 2016.

In light of the narrowing political space, many say civil disobedience is the only viable channel through which to demand change. However, despite the initial success of social media in mobilising some segments of society, activists fear the movement could soon fizzle out.

“There cannot be a hashtag revolution in Sudan,” said Mohammed Naji, a young doctor and activist in Khartoum. “If there is no clear plan for the people, by a body they know, organising them and leading them to change, I doubt that this movement will continue.”

In weighing the campaign’s chances of success, Naji points to Sudan’s 1964 and 1985 revolutions, when professional and student unions took the lead in rallying the population to demand regime change. Back then, unions wielded vast influence over society, organising shutdowns and public demonstrations that paralysed the country, eventually prompting the military to step in and call for fresh elections.

When Bashir took power in 1989, the unions were dismantled or placed under the control of the ruling party, smothering what was once a vibrant civil society.

“The regime [knows] that if there is danger for them, it will be from the professional organisations because history says that,” said Naji.

Yet there are signs that professional sectors are beginning to organise again, albeit in an informal way.

President Omar al-Bashir attends the new legislative session at the parliament in Khartoum in October 2016. Photograph: Ebrahim Hamid/Anadolu/Getty Images

Recently, Naji helped to mobilise doctors across Sudan to demand more resources for the public healthcare sector. Using social media, the Central Committee for Doctors organised a series of strikes in October and November. More than 100 doctors were reportedly arrested, but eventually the government released the detainees and agreed to address their grievances. The doctors’ initiative prompted other professionals to follow suit and served as a catalyst for the 27 November call for civil disobedience.

“We saw it as a victory,” said Naji. But much more would need to be done to bring about meaningful change, not least mobilising Sudan’s rural population and uniting Sudan’s disjointed opposition to build a political platform for the way forward. Only then, Naji believes, would people be willing to take to the streets once again.

“If we get to the street without organisation, without having a clear plan, I think we will lose,” said Naji at the end of 2016. “We have been patient for 27 years. We can be patient for a few more months.”

• Simona Foltyn’s reporting from Sudan was funded by The Investigative Fund at the Nation Institute