CHIMANIMANI, Zimbabwe — When the mudslide struck, students at the St. Charles Lwanga School had nowhere to go. So they waited for days with their classmates’ corpses, hoping for rescue.

The survivors huddled together in dining halls and classrooms at their boarding school in eastern Zimbabwe, waiting out the aftermath of the devastation wrought by Cyclone Idai in Mozambique and neighboring countries — and waiting for help as they mourned two students and a security guard who were crushed to death on Friday evening.

Two days passed before a group of students finally braved the treacherous conditions and walked for miles, taking turns carrying the dead in makeshift coffins until they reached safety.

More than 300 people in Mozambique, Zimbabwe, Malawi and elsewhere in the region have been declared dead since Idai came ashore near the central Mozambican port city of Beira on Friday, destroying infrastructure across the city of half a million.

The cyclone brought severe rain and winds exceeding 100 mph, and road and weather conditions slowed the disaster response — leaving the most affected communities in limbo. Although aid is now trickling into Zimbabwe, boulders from mudslides are still blocking some roads. Floods washed away bridges that connect a number of the most devastated areas, forcing some military and aid workers to move by foot.

High floodwaters have made aid distribution difficult in Mozambique.

Even more rain is expected for the region, raising fears that more severe flooding could be on its way and that waterborne illnesses could spread quickly at a time when health resources are already spread thin.

Many did not evacuate before the storm came ashore, wreaking havoc across the region. Houses are destroyed, and survivors had to scramble to their roofs and hope to be rescued.

“If we had closed schools, we would have saved lives,” Minister of Local Government July Moyo told reporters Tuesday in the Zimbabwean capital, Harare.

Nyevero Sinyabuwe survived the storm’s arrival in Zimbabwe, but two of her children were killed when a boulder rolled on top of their hut in Ngangu township. She called for help, she said, “but it was too late.”

Hundreds of people are missing and the death count is expected to rise in all the countries affected, as rescue workers gain access to remote areas cut off by rain, flooding and damaged roads.

“We understand there are bodies which are floating,” Moyo said. “Some are floating all the way into Mozambique.”

Sinyabuwe said that as people fled the worst-hit regions in Zimbabwe, near the border with Mozambique, they were forced to leave behind the dead. She fears her children are among those whose bodies may never be recovered. Many others may now be buried in mass graves, she said.

Three days of mourning for the cyclone’s victims started Wednesday in Mozambique.

Mozambican President Filipe Nyusi said late Tuesday that more than 200 people died in Mozambique alone. The day before, after flying over the hardest-hit region, he estimated that as many as 1,000 may have been killed. Rescue teams are fanning out in boats and helicopters into Beira and surrounding towns to rescue those clinging to rooftops and palm trees above the rising floodwaters.

“Many people are in a desperate situation, fighting for their lives at the moment, sitting on rooftops in trees and other elevated areas — this includes families and obviously many children,” UNICEF spokesman Christophe Boulierac said in a video released Wednesday.

Beira’s airport is one of the few areas still above water, making it a natural staging ground for aid sent from around the world.

The U.N. World Food Program, which rushed four tons of high-energy biscuits to Beira on Monday, has been distributing emergency food supplies and water to people in the area. Starting Wednesday, it began reaching areas inland from Beira.

“WFP is starting food distributions in Dondo today outside Beira,” said Deborah Nguyen, part of the WFP response in the port city. “Communities stranded by floods in Buzi and surroundings are being rescued by helicopters to Beira for now,” she added, referring to the area across the river from the port where thousands of people are believed to be stranded and which the United Nations has warned risks being submerged.

She said there has been no letup in the rain, which has turned large parts of the country into an inland sea.

The government estimates that about 400,000 people have been displaced, but WFP said that about 1.7 million people were in the cyclone’s path and that “the extent of the human suffering is not known.” Given the vast size of the affected region, “we do expect the death toll to increase significantly,” the agency said.

The European Union said it was releasing $3.9 million in emergency aid, while Britain has pledged $7.9 million.

The United Arab Emirates announced that it was sending about $5 million in emergency aid including food supplies, supplements for children, medicine and shelter supplies for 600,000 people across Mozambique, Malawi and Zimbabwe. It said it would also send Red Crescent delegations to assess the situation on the ground “so that further assistance plans” can be implemented.

Three Indian navy ships also diverted to Beira, arriving Tuesday and distributing food, medicine, clothing and water. The Indian navy said it was assisting with evacuations.

Beira, Mozambique’s second-largest port, is a major gateway not only to the center of the country but also for landlocked Zimbabwe and Malawi.

The cyclone was particularly devastating for the impoverished region and its poor infrastructure because the storm’s meandering path meant it made landfall twice — first as a tropical depression and then, 11 days later, as a Category 2 cyclone.

The storm has also been blamed for 10 deaths in South Africa and Madagascar.

Schemm reported from Addis Ababa, and O’Grady from Washington.