Some armed with two 21-inch (530 mm) torpedoes, possibly in drop collars.
First successful indigenous midget submarine
The Yugo class submarine is a class of four midget submarines used primarily for infiltration and espionage by North Korea. The class is so named because it was built to plans supplied to North Korea by Yugoslavia in 1965. This class is a family of midget submarines which are not all identical. The displacement is either the standard 90 tons of the original Yugoslavian design for the early units, or 110 tons for the later units, while armament is either a pair of 400 mm torpedo tubes (early units) or a pair of 21 in short torpedo tubes (later units); however, all units have the same range: 550 nautical miles (1,020 km) at 10 knots (19 km/h) on the surface and 50 nautical miles (93 km) at 4 knots (7.4 km/h) submerged. The final example was built in the 1980s, after which they were superseded by the Sang-O class submersibles. In 1998 one out of 6 submarines was captured by the South Koreans. In July 2007, 4 were transferred to Iran to repay part of North Korea's debts to Iran, the last one was retired but kept by the North Koreans.
In March 2016, it was announced that the North Korean Navy had lost one of the ships during exercises.
A variation of the Yugo class has been spotted in La Havana harbour, Cuba. Only a single vessel has been seen, and it is unknown the actual number of units and the key differences with the original Yugo. Rumored to be named "Delfin", it's unknown if it was built in North Korea, or in Cuba with Korean assistance.