Yono-class submarine

The Yono class submarine (also as Yugo Class) is a class of North Korean miniature submarines, produced for domestic use as well as for export. Also referred to as Yeono class vessels, these submarines displace 130 tons, significantly less than North Korea's larger 1,800-ton Romeo class submarines. As of May 2010, North Korea is reported to operate 10 of these submarines.

Combat involvement
A Yono class submarine is thought to have fired the torpedo attack which sank a South Korean Pohang-class corvette, the ROKS Cheonan on March 26, 2010 in South Korean waters. According to some investigators, the weapon used in the attack was a North Korean-manufactured CHT-02D torpedo, from which substantial parts were recovered. The device allegedly exploded not by contact, but by proximity, creating a powerful pillar of water, called the bubble jet effect. High ranking North Korean military officials denounced the international investigation and said the North does not have the type of submarines that supposedly carried out the attack. They also dismissed claims regarding writings on the torpedo and clarified that "when we put serial numbers on weapons, we engrave them with machines." South Korea’s Yonhap News quoted South Korean officials as saying the North has about 10 of the Yeono class submarines.

Export and foreign production
The US Congressional Research Service suggests that Iran has purchased several midget submarines from North Korea. The purchase may have involved Yono class and Yugo class mini-subs. Beginning in 2006, Iran launched the first of several domestically-produced mini-subs. In 2007 the Iranian navy unveiled its Qadir (Ghadir) class submarine, the first of a number of planned midget submarines of the Yono class. Observers have disagreed on the exact classification of the Iranian derivative: Iran claims the vessel is a fully independent design, but it has been compared to the North Korean Yugo boats, Yono subs, and/or Sang-O Class coastal submarines.