The masked militants stormed the halls of the College of Education building at Yemen's Aden University, attacking staff members and posting stark warnings of consequences for failure to comply with Islamic law.
"The Mujahideen brothers of the Islamic State hold you responsible for [this]," admonished the leaflet, an image of which quickly spread on social media.
"If you do not comply, know that we will rip your heads from your bodies, turn your bodies to ash, and make your buildings rubble before the whole world."
The incident last month was just one more threat to civilians since the start of a punishing air campaign by a Saudi-led coalition last March aimed at driving rebels from the minority Houthi sect out of Sana, the Yemeni capital, and reinstating Saudi-backed President Abed Rabbu Mansour Hadi.
Human rights monitors and others say the Saudi-led campaign -- backed by intelligence from Washington -- has led to thousands of civilian casualties, destroyed much of the impoverished nation's infrastructure and proved a boon for Al Qaeda in the Arabian Peninsula, widely viewed as Al Qaeda's most potent franchise -- and an enemy of both the Saudi Arabian government and the Houthi rebels.
With lawlessness on the rise, Yemen now also hosts a newly minted franchise of Islamic State, the Al Qaeda breakaway group that a U.S.-led coalition is bombing in Syria and Iraq.
Al Qaeda and Islamic State remain fierce rivals here, and Al Qaeda, with years of experience in Yemen, is by far the more potent force. Saudi Arabia rejects criticism that its actions have enabled the rise of the militant groups and regards both Al Qaeda and Islamic State as terrorist organizations.
This is a strategically situated nation that the Obama administration once cited as an example of the success of its counter-insurgency strategy.
Yet while wars in Syria and Iraq -- with profound geopolitical implications for the future of the Middle East -- remain center stage in global attention, the crisis in Yemen has largely fallen off the map, a forgotten war with a daily roster of destruction and civilian deaths.
"Yemen is in an all-out war, in which the population caught on the wrong side is considered a legitimate target," Hassan Boucenine, head of mission in Yemen for Doctors Without Borders, said in a statement published Tuesday.
"Markets, schools, roads, bridges, trucks transporting food, displaced persons' camps, and health structures have been bombed and destroyed. And the first victims are civilians," he said.
Almost half of the more than 5,600 people killed in the conflict since March have been civilians, with approximately two thirds of those deaths caused by air strikes by the Saudi-led coalition, the office of the U.N. High Commissioner for Human Rights said last week.
The Houthis and forces loyal to former Yemeni President Ali Abdullah Saleh -- now allied with the Houthis -- were responsible for most of the remaining fatalities, the United Nations said. There have been no official estimates of casualties attributed to Al Qaeda and its spinoffs.
Civilians are also facing severe shortages of food and water as a result of a Saudi blockade on Yemen's ports and airports. With more than half of the country's population defined as "food insecure" even before the war, the crisis has pushed already tattered basic services to the brink of collapse. Officials fear spreading hunger, especially among the country's large and vulnerable youth population.
"Millions of Yemenis are in desperate need of food assistance, as well as nutritional support for their children to survive," U.N. Humanitarian Coordinator Johannes Van Der Klaauw said in a statement published last week.
Apart from the humanitarian costs, the crisis has also nudged Yemen's ever-precarious economy into freefall. Production of oil and gas has largely ceased; assistance by foreign aid agencies and donors, pivotal to projects throughout the country, has been all but suspended; and the local currency has been plummeting in value.
Saudi officials deny targeting civilians in their more-than-seven-month campaign, which also includes allied ground forces from the United Arab Emirates and Qatar, a pair of Gulf partners of Riyadh.
"We are very careful in picking targets," Saudi Foreign Minister Adel al-Jubeir told CBS News in a September interview. He spoke after a coalition bombing struck a wedding party, killing 38 civilians.
"We work with our allies, including the United States, on these targets," he said.
Collateral damage to civilians was "extremely regrettable" and should be minimized, Jubeir said.
"But can we prevent it 100%? I don't think you can. This is warfare," he said.
Last week, warplanes from the Saudi-led coalition pounded a field hospital in the town of Haydan, west of the northern city of Saadah, a Houthi stronghold.
The staff evacuated the hospital with seconds to spare before coalition planes came to finish the job with a second bombing run. Saudi forces denied having bombed the hospital.
In coastal Aden, where Saudi-led forces established a beachhead in July after wresting control of the city from the Houthis, residents speak of cars adorned with jihadist black-on-white flags driving through the city with impunity.
The Islamic State militants who stormed Aden University decreed there would be no more celebrations that featured music, and that all faculty and students would have to attend daily prayer, among other new Islamic restrictions.
"They said to separate the women from the men, and that they will no longer be allowed to mix," said Slams Essa, a hospital nurse contacted by phone.
Saudi-backed forces in Aden appear to be concentrated near the strategic airport, leaving much of the city lawless, said Yemeni journalist Abdul-Raqib Hedyan, contacted by phone in Aden.
Reports in Aden indicate that Al Qaeda and Islamic State forces have commandeered dozens of armored cars and military vehicles, he noted. Last month, presumed Al Qaeda-linked forces broke into a high-security prison near Aden and sprang a prisoner suspected of an assassination attempt against the township's former governor. Jihadists also reportedly stormed a high-end supermarket in Aden, firing shots in the air and shouting at women to cover their faces with veils.
"The extremists are attacking places every day," Hedyan said, "and there is no one to fight them."