The notices - a copy of which was obtained by the Thomson Reuters Foundation - ordered residents whose houses had been built without official permits to demolish them within seven days.
Those who refused would be taken to court, the notice said. There would be no compensation.
The news sparked worry and anger among residents, many of whom had arrived in the boomtown in Ethiopia's Oromia region a decade or so ago, but never formally registered the homes they built.
As a shortage of land and affordable housing has led to an explosion of settlements on the edges of major towns, anxiety is particularly acute among Oromia residents, where authorities began targeting informal housing earlier this year.
"If they demolish the house, I cannot imagine what I'll do - I can't afford to build another," said Sululta resident and mother-of-five Tigust Mekuria.
"It would be better to kill us than to displace us," she told the Thomson Reuters Foundation in the living room of her family home, her severely disabled daughter lying on her lap.
According to Tigust's neighbour, Tsegaw Asfaw, a group of more than 200 Sululta residents tried travelling to Addis Ababa two days after the eviction notices went up to complain to regional authorities, but were stopped by police en route.
Since then, they say, they have heard no word from the government and have no idea when demolitions will begin.
"We are still waiting," Tsegaw said. "We are in a situation of fear and uncertainty."
Regional government spokesman Admassu Damtew said in a phone interview that "the (Oromia) regional government is clamping down as part of efforts to ensure the rule of law in towns where illegal settlement is very high."
In Sululta, the city's authorities have said the illegal settlements encroach on planned green areas, market places, forests and land earmarked for investors.
The city's mayor, Rosa Umar, told the Thomson Reuters Foundation that a team of experts was assessing which houses would be torn down, adding that though she did not yet know the total, it could be as many as 30,000.
"If the houses are illegal, they have to be demolished," she said in a phone interview.
She said evictions would begin after the assessment had been concluded, and that there would be a public information campaign to explain the reasons behind the programme.
LAND RUSH
Satellite towns like Sululta have been on the frontline of a land rush over the past decade, as real estate speculators and low-income households looking for cheap land move from the capital into surrounding Oromia.
"People were desperate for land," said Daniel Behailu, a land governance expert at Ethiopia's Hawassa University. "They went marching into the peri-urban areas."
In Ethiopia, all land is owned by the state. While buying and selling it is illegal, long-term leases can be bought from the government.
But homeowners and land law experts say that, in practice, there is a bustling underground market facilitated by developers, brokers and local officials, who often turn a blind eye to illegal activity.
"They (the authorities) were very silent when we were building the houses," said Sebehat Worku, another Sululta resident, adding that officials had never asked to see any title deeds before last month.
He and other residents said that officials had never asked them to show their title deeds before last month and had instead helped bring electricity, water and road infrastructure to the neighbourhood.
The head of land use and administration for Oromia, Milkessa Midega, did not respond to several requests for comment.
BUILDING ON HOPE
Farmers around Sululta have long been selling chunks of their plots to newcomers, convinced that the land will eventually be expropriated by the government as the district urbanises, said Mekonnen Firew Ayano, a lawyer and researcher at Harvard Law School.
"They (settlers) know that it is illegal" to build on that land, said Mekonnen, who specialises in Ethiopian land law. "But they hope that one day the municipality will legalise it."
That hope is based on precedent.
In 2015, Addis Ababa authorities tried to tackle the boom in illegal housing by granting almost 45,000 title deeds to people who had built homes on common land or on plots that belonged to farmers, Mekonnen said.
But those instances are rare, according to Mekonnen and other land experts in Ethiopia, who said demolition is much more common.
LACK OF TRUST
Residents say they have little trust in the authorities' motives, a feeling that has become more widespread in the past year amid an ongoing dispute over the constitutional status of the Ethiopian capital, said Mekonnen, the Harvard lawyer.
Many Oromo activists and politicians argue that Addis Ababa should be under Oromo jurisdiction, since it is located entirely within the Oromia region.
Opponents say that as a federal capital with a multi-ethnic population – of which Oromos make up only about 20 percent, according to the latest census in 2007 - the city should remain under federal jurisdiction.
Lemma Megersa, who was Oromia regional president until last week, told journalists in December that over the past year, his administration had resettled more than half a million Oromos displaced by conflicts in other parts of the country to towns around Addis Ababa, including Sululta.
This has contributed to suspicions among residents of the capital that the region's ruling party, the Oromo Democratic Party, is trying to alter the demographics of the city and its surroundings in favour of the Oromo.
Both Lemma and the country's new prime minister Abiy Ahmed, an Oromo, have publicly denied the allegations.
But, Worku Tsedeke, a Sululta resident leading efforts to petition the mayor against the evictions, believes that is what is happening right now in his neighbourhood.
"Those targeted (for eviction) are mostly from other parts of the country," he said.
"I see this as racism."
A WORKABLE SOLUTION
Experts are divided on whether mass legalisation of informal settlements, a provision of a 2011 urban land law, could be a workable solution.
"The cost and insecurity of demolishing is much more expensive than regularising," said Daniel, the land governance expert.
"It does not help to stop squatting," he added.
But Mekonnen warned that would only provide a short-term fix.
"Blank-cheque legalisation sets a precedent that is likely to create more problems," he said.
Instead, he added, farmers need guarantees that officials will not decide arbitrarily to expropriate their land so they no longer feel the need to sell it off in pieces, while the concerns of settlers "should be addressed through better housing policies".
Birhanu Lenjiso, deputy director of the California-based East African Policy Research Institute, agreed, and said that alternative settlement schemes should be put in place before any homes are demolished.
"Local officials allowed land to be sold illegally to these settlers, then came later and evicted them," he said."They are responsible for this mess."