Australian junior world No.1 Nick Kyrgios has suffered a surprise defeat in the second round of the French Open boys’ singles.

The top seed went down 6-2 6-7 (8-6) 6-3 to unseeded Russian Karen Khachanov on Monday.

It was his first singles loss in juniors since September and ended hopes of winning back-to-back grand slam boys titles after his triumph at the Australian Open.

Kyrgios, 18, was hot favourite for the title after reaching the second round of the men’s event last week by beating Czech veteran Radek Stepanek.

Fellow Australian Bradley Mousley was also beaten on Monday to leave no Australians left in the junior competitions at Roland Garros.