UNITED NATIONS - The number of confirmed deaths from Cyclone Idai in southern Africa has risen to at least 437 with officials expecting the death toll to rise further, a UN official said on Thursday.

In Mozambique, "the death toll has now risen to 242," said Gemma Connell, head of the UN Office for Coordination of Humanitarian Affairs' (OCHA) Regional Office for Southern and Eastern Africa, in the Mozambican capital of Maputo.

More than 195 people died in neighboring Malawi (56) and Zimbabwe (139), according to the respective governments, she said in a telephone briefing for reporters.

"We do anticipate for that to rise in the days ahead as the full extent of the loss of life becomes known," she said. "It's critical for everyone to be aware that many areas remain inundated with water and therefore the counting of the dead will continue to take some time, so we expect the death toll to rise as that progresses.

Connell said that on Wednesday she was in Beira, a flooded port city of about 500,000, and toured some of the region by helicopter, where roads were mostly impassible.

Beira is a key gateway for neighboring and landlocked Malawi, Zambia and Zimbabwe where Idai made landfall on March 15.

"When I was over the area of Buzi (a nearby district), we were starting to see some of the flood waters beginning to go down," she said. "There is still the possibility of secondary floods."

"Therefore, we are on high alert for this situation to worsen," the aid worker said. "But, we are happy that we have the good news of the flood waters going down."

The OCHA official lauded two key non-governmental organizations (NGOs) providing air support for the relief operation, Mercy Air and Wings Like Eagles, calling helicopter crews "heroic," and saying it was "absolutely critical" to have the air support.

She said OCHA was not seeking supplies but needed more funds.

The head of OCHA, Undersecretary-General Mark Lowcock, announced earlier in the week 20 million US dollars had been freed from the UN's Central Emergency Relief Fund. Connell said that was not near enough.

She said high energy biscuits and clean drinking water had initially been provided to flood victims, many of whom had gathered in houses of worship, stadiums and other large sites above the water.

Idai, as a tropical storm, flooded parts of central Mozambique and southern Malawi in early March, meteorological agencies said. It then went back out to sea, gathered strength and doubled back as a full-fledged cyclone to hit many already flooded areas.

The OCHA regional head said Cyclone Idai had created a "complex situation and an even more complex (humanitarian) response".