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 200 people in Mozambique, 98 in Zimbabwe, and 120 in Malawi 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 storm brought severe rain and winds exceeding 100 miles per hour, and road and weather conditions slowed the disaster response. Although aid is now trickling in, boulders from mudslides are still blocking some roads. Floods washed away bridges that connect a number of the most affected areas, forcing military and aid workers to move by foot.

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,’’ local government minister July Moyo told reporters in the Zimbabwean capital, Harare, on Tuesday.

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 of Mozambique, they were forced to leave behind bodies of the dead. She fears her children are among those whose bodies may not be recovered. And many others may now be buried in mass graves, she said.

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

Mozambican President Filipe Nyusi said late Tuesday that more than 200 people have been declared dead.

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.

The UN World Food Program, which rushed 4 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.

The government has estimated that about 400,000 people have been displaced and the UN program 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.

Meanwhile, rain has continued to fall.