Chinese official media said that a nuclear submarine of the People's Liberation Army (PLA) Navy accompanied the anti-piracy mission in the Gulf of Aden patrolled the area for more than two months, escorting two ships and a supply vessel.
The submarine stated to be Type 091 has since returned to its base in Qingdao, Shandong province.
CCTV interviewed Deputy Commander Yu Zhengqiang, who said the crew had to overcome many obstacles during the mission.
Military analysts said the deployment would cause unease among China's neighbours.
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Beijing may deploy more vessels to far-flung regions as it broadens its political and investment interests overseas, it said.
Hsieh Tai-hsi, secretary general of the Taipei-based Society for Strategic Studies, said the deployment would concern both the United States and countries in the region, particularly India.
He said India was already concerned about Pakistan's deal to buy eight Chinese submarines and China's involvement in port projects in South Asia.