(Reuters)

Since Cyclone Idai roared into the Mozambican port city of Beira on Mar. 14, devastating losses are mounting exponentially yet international aid has been slow to reach all survivors.

Severe flooding produced by Idai’s strong winds and heavy rains caused the rivers Pungwe and Buzi to break their banks. In the district of Buzi, thousands clung for their lives on trees and rooftops, as their villages turned into an ocean. Even as the rains have subsided and the waters are receding, the risk of flooding remains, as dams upstream reach full capacity.

At least 656 people have died across three countries, according to local estimates.

Dire shortages of food, water and other necessities were reported by the head of a South African rescue operation. Around 15,000 people are still missing, Land and Environment Minister Celso Correia said just before last weekend.

But delays in the arrival of assistance were fueling anger and desperation, acknowledged Connor Hartnady, rescue operations task force leader for Rescue South Africa.

“There have been three security incidents today, all food related,” he told his team, without giving further details.

The U.N. has made an emergency appeal for $282 million for the next three months to help Mozambique start rebuilding their communities.

But help has been coming in dribs and drabs – especially from those with the most resources. U.S. military personnel, for example, were en route to Mozambique on Monday, over a week after the cyclone hit, to assess damage and plan a relief mission aided by U.S. Africa Command (AFRICOM).

The Pentagon has authorized AFRICOM to expend up to $6.5 million in relief funds to provide logistics support for up to 10 days. The military’s role will be to assist the U.S. Agency for International Development in the delivery of humanitarian assistance.

Two Portuguese Airforce C130 transport planes were due to depart Thursday to the region. The first one was taking 35 soldiers, medical personnel and a disaster relief team from the National Republican Guard.

Mozambique is home to thousands of nationals from Portugal. Santos Silva said that 30 of the country’s citizens had not yet been contacted.

U.N. humanitarian chief Mark Lowcock said funds for cyclone victims are starting to come through, including 29 million dollars from the United Kingdom, but this is far exceeded by the need.

Finally, ExxonMobil, which earned $6 billion in quarterly profits from African oil, is donating $300,000 for disaster relief.   “The devastation has been widespread,” the company tweeted, “and this funding will help provide relief during a difficult time. Our thoughts are with everyone affected.”