MANILA — Rising tensions in the South China Sea have turned Vietnam into one of the world’s most active arms importers, with Hanoi buying more weaponry than wealthy neighbors South Korea and Singapore as it tries to counter China’s increasingly aggressive territorial claims.

Tiny Vietnam was the world’s eighth-largest arms importer from 2011-2015 — a huge leap from the previous five-year period when it was in 43rd place, according to the latest annual study of global arms-trade patterns by the Stockholm International Peace Research Institute, a security think tank. Vietnam accounted for roughly 3% of world-wide arms purchases between 2011 and 2015, the study, released Monday, shows.