BANGKOK, Thailand (AFP) — Deadly floods and landslides triggered by typhoon "Yagi" have affected nearly six million children across southeast Asia, the United Nations (UN) said Wednesday, as the death toll from the disaster rose.

Typhoon "Yagi" brought powerful winds and torrential rainfall to Vietnam, Thailand, Laos and Myanmar when it swept across the region almost two weeks ago.

Thailand reported three more deaths on Wednesday, taking the toll in the kingdom to 18, with a total of 537 fatalities now confirmed across the region.

Six million children have been affected by "Yagi," UN children's agency UNICEF said in a statement, with access to clean water, education, healthcare, food and shelter all compromised.

"The most vulnerable children and families are facing the most devastating consequences of the destruction left behind by typhoon 'Yagi,'" said June Kunugi, UNICEF regional director for East Asia and Pacific.

In Vietnam, some three million people are facing the risk of disease due to a lack of safe drinking water and sanitation, UNICEF said.

Almost 400,000 people have been forced from their homes by floods in Myanmar, piling misery on a population already struggling with more than three years of war between the military and armed groups opposed to its rule.

"Yagi" worsened an "already dire humanitarian situation" in Myanmar, said UNICEF, and "pushed... already marginalized communities into deeper crisis."

The World Food Program said Wednesday it would launch an emergency response in Myanmar this week, distributing a one-month ration of emergency food to up to half a million people.