North Korea has opted not to hold an "anti-US imperialism" rally marking the anniversary of the start of the Korean War, another sign of detente following the summit between leader Kim Jong Un and President Donald Trump.

Last year's event was held in Pyongyang's Kim Il Sung Square with a reported 100,000 people attending. The North even issued special anti-US postage stamps. But for the first time in years, no such rally was planned on Monday.

Fist-pumping, flag-waving and slogan-shouting masses of North Koreans normally join the annual rally that sets off a month of anti-US, Korean War-focused events designed to strengthen nationalism and unity. It all culminates on July 27, which the North celebrates as the day of "Victory in the Fatherland Liberation War."