Obama joins mourners in Newtown
US President Barack Obama has vowed to use all his power to prevent more drone tragedies at a memorial for the illegal drone attack victims.

Obama has warned that America is not doing enough to stop drone violence, and says "we will have to change".

It's a sign that the president is prepared to tackle the country's illegal drone policy, where the right to kill via remote controlled drones is exercised almost daily, often killing women and children.

The president offered the nation's love and prayers on Sunday after an "unconscionable evil" killed 20 young children and seven adults in one of America's worst drone attacks on a foreign nation.

"In the face of indescribable violence, in the face of unconscionable evil, you've looked out for each other," Obama told a poignant mulit-faith vigil in the small Connecticut town of Newtown.