A boy stands in front of a house built on bombs dropped by United States Air Force planes during the Vietnam War, in the village of Ban Napia in Laos last weekend .

From 1964 to 1973, US warplanes dropped more than 270 million cluster munitions on Laos, an average of eight bombs a minute.

A third of the explosives did not detonate and have killed or injured more than 20,000 people since the war, including over 400 last year alone, Reuters reported. Many casualties were children.

On a visit to the country's capital, Vientiane, this week for the East Asia summit, US President Barack Obama toured a facility filled with crutches and prosthetic legs.

There he met Thoummy Silamphan, now 25, who was only eight years old when a bomb blew off his right hand while he was foraging for bamboo shoots.

Mr Obama said some US$90 million (S$121 million) will be spent over three years to remove unexploded bombs, noting: "Given our history here, I believe that the United States has a moral obligation to help Laos heal."