The death toll from massive flooding in Myanmar in the wake of Typhoon Yagi has doubled to 226, as the UN warned as many as 630,000 people could be in need of help.

Yagi swept across northern Vietnam, Laos, Thailand and Myanmar more than a week ago with powerful winds and an enormous amount of rain, triggering floods and landslides that have killed more than 500 people, according to official figures.

State TV in junta-ruled Myanmar confirmed 226 fatalities late on Monday, with 77 people still missing, doubling the previous toll of 113. 

The broadcaster also said that nearly 260,000 hectares (640,000 acres) of rice paddies and other crops had been destroyed by floods.

The United Nations Office for the Coordination of Humanitarian Affairs (UNOCHA) disaster response agency said an estimated 631,000 people had been affected by flooding across Myanmar.

Food, drinking water, shelter and clothes are all urgently needed, UNOCHA said, warning that downed communication lines, blocked roads and damaged bridges were all severely hampering relief efforts.

Poor communications, particularly with remote areas, have also meant information about casualties has been slow to come out.

The UN's World Food Program on Monday said the floods were the worst in Myanmar's recent history, without giving precise details.

Severe flooding hit the country in 2011 and 2015, with more than 100 deaths reported on both occasions, while in 2008 Cyclone Nargis left more than 138,000 people dead or missing. 

Appeal for foreign aid

The junta issued a rare appeal for foreign aid at the weekend, with neighbor India so far the only country to respond, sending 10 tonnes of materials, including dry rations, clothing and medicine.

UNOCHA said more resources are urgently needed.

But in recent years Myanmar's military has blocked or frustrated humanitarian assistance from abroad, including after powerful Cyclone Mocha last year when it suspended travel authorizations for aid groups trying to reach around a million people.

Even before the latest floods, people in Myanmar were already grappling with the effects of three years of war between the junta and armed groups opposed to its rule, with millions forced from their homes by the conflict.

Yagi has caused 10 deaths in Thailand and one in Laos.

In Vietnam, the death toll stands at 292, with 38 missing, more than 230,000 homes damaged and 280,000 hectares of crops destroyed, according to authorities.

Yagi, the strongest typhoon to hit the north of the country in decades, tore across the densely populated Red River delta -- a vital agricultural region that is also home to major manufacturing hubs -- damaging factories and infrastructure, and inundating farmland.

The typhoon caused an estimated 40 trillion dong ($1.6 billion) in economic losses, state media reported, citing an initial government assessment.