US president Barack Obama lays a wreath at the Hiroshima Peace Memorial Park and Museum in Hiroshima, Japan, May 27, 2016. [Photo/IC]

HIROSHIMA, Japan - Barack Obama, the first incumbent US president to visit Hiroshima, laid a wreath at the site of the world's first atomic bombing on Friday, a symbolic gesture that Tokyo and Washington hope will highlight their alliance and breathe life into efforts to abolish nuclear arms.

The atomic bomb dropped on Hiroshima on Aug 6, 1945, killed thousands of people instantly and some 140,000 by the year's end. The city of Nagasaki was hit by a second bomb on Aug 9, 1945 and Japan surrendered three days later.

A majority of Americans see the bombings as having been necessary to end the war and save lives. Most Japanese believe they were unjustified.