A recent joint China-Iran-Russia navy exercise in Gulf of Oman enhanced the ability of the navies to conduct diversified maritime missions, China's defense ministry said on Thursday. The drills further deepened friendship and practical cooperation among the three countries, said Tan Kefei, a ministry spokesman. The three nations sent forces including 12 ships, special operations and diving units to participate in the drills from March 15 to 19, Tan said.