Patrol service of North Vietnamese navy according to the Australia Station Intelligence Summary dated 8 May 1957

An item reported that the North Vietnamese navy possessed 4 patrol units each consisting of 1 patrol vessel and 10 armed motor launches with the main intercepting refugees who wanted to escape to South Vietnam. Patrol areas were Mon Cay-Hongay, Hongay-Do Son, Do Son-Sam Son and Sam Son-Ben Thuy.

Source

Website Royal Australian Navy, Sea Power Centre.