Chimanimani, Zimbabwe — Rapidly rising floodwaters have created "an inland ocean" in Mozambique endangering many thousands of families, aid workers said Tuesday as they scrambled to rescue survivors of Cyclone Idai who clung to rooftops and trees. Hundreds were dead, many more were missing and thousands were at risk in Mozambique, Zimbabwe and Malawi. Mozambique's President Filipe Nyusi has said the death toll could reach 1,000.

Emergency workers called it the region's most destructive flooding in 20 years. Heavy rains are expected to continue through Thursday.

Rush to help survivors

"This is a major humanitarian emergency that is getting bigger by the hour," said Herve Verhoosel with the World Food Program. Many people were "crammed on rooftops and elevated patches of land outside the port city of Beira" and WFP was rescuing as many as possible and airdropping food, water and blankets, he said.

Get Breaking News Delivered to Your Inbox

Mozambique's Pungue and Buzi rivers had overflowed, creating "inland oceans extending for miles and miles in all directions," Verhoosel said. Dams have reached 95 percent to 100 percent capacity.

"People visible from the air may be the lucky ones and the top priority now is to rescue as many as possible," he said.

The extent of the damage was not yet known as many areas remained impassible. With key roads washed away, aid groups were trying to get badly needed food, medicine and fuel into hard-hit Beira, a city of some 500,000 people, by air and sea.

Cyclone Idai swept across central Mozambique before dropping huge amounts of rain in neighboring Zimbabwe's eastern mountains. That rainfall is now rushing back through Mozambique, further inundating the already flooded countryside.

A man stands on the edge of a collapsed bridge in Chimanimani, about 400 miles southeast of Harare, Zimbabwe, March 18, 2019, after Cyclone Idai devastated the region. AP

"It's dire," Caroline Haga of the Red Cross told The Associated Press from Beira. "We did an aerial surveillance yesterday and saw people on rooftops and in tree branches. The waters are still rising and we are desperately trying to save as many as possible."

Satellite images were helping the rescue teams to target the most critical areas, Haga said. Rescue operations were based at Beira airport, one of the few places in the city with working communications.

The waters flooded a swath of land more than 30 miles wide in central Mozambique, said the aid group Save the Children, and more than 100,000 people were at risk.

"The assessment emerging from Mozambique today is chilling," said Machiel Pouw, Save the Children's response leader in Mozambique. "Thousands of children lived in areas completely engulfed by water. In many places, no roofs or tree tops are even visible above the floods."

Torrential rain was still lashing the region, and Buzi town could be entirely submerged within 24 hours, the aid group said.

Ground-zero: City of Beira

Hardest hit is Beira, where thousands of homes have been destroyed.

The city and surrounding areas have no power and nearly all communication lines have been destroyed. Beira's main hospital has been badly damaged. The cities of Dondo and Chimoio are also badly affected.

Beira could face a "serious fuel shortage" in the coming days, WFP said, and its power grid is expected to be non-functional through the end of the month.

In Zimbabwe the death toll rose to 98, the government said. The mountain town of Chimanimani was badly hit. Several roads leading into the town were cut off, with the only access by helicopter. Residents expected the death toll to rise.

"We did over 38 burials this morning," Absolom Makanga, a Salvation Army divisional commander, told the AP. "It is difficult. We have to walk long distances because the roads are cut off but also because sometimes the graves are then washed away."

Helicopter footage shows flooding and damage after Cyclone Idai in Beira, Mozambique, March 17, 2019, in this still image taken from a social media video on March 18, 2019. Social Media

Luckmore Rusero carried a small bag with his remaining possessions. His wife carried their 1-year-old child while their 11-year-old son struggled to keep pace as they joined many others in seeking refuge.

"Thank God we survived. There are no roads, no transport, so we have been walking for more than 20 kilometers now through the forests and the mountains," Rusero said.

Some escaped with nothing but their lives.

"I fled naked," Tecla Chagwiza said. "I only received clothes in the morning from well-wishers who are also helping me with food." She said her family's home was destroyed and three neighbors were dead. Others were missing.

President Emmerson Mnangagwa arrived in the area on Tuesday, saying a number of countries including the United Arab Emirates, South Africa, Botswana, Namibia and Angola were offering aid.

Malawi's government has confirmed 56 deaths, three missing and 577 injured in the severe flooding. Rivers have burst their banks, leaving many houses submerged and around 11,000 households displaced in the southern district of Nsanje.

Neighboring Tanzania's military airlifted some 238 tons of emergency food and medicine to the three countries.