Chinese official media said that a nuclear submarine of the People's Liberation Army 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.
“First, there were concerns about all the equipment and facilities, and second [we had to] deal with various challenges while sailing in totally unknown waters, which was complicated by military intelligence issues,” Hong Kong-based South China Morning Post quoted Yu as saying.
Military analysts said the deployment would cause unease among China's neighbours.
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.
"But more importantly, through the mission, the PLA was able to cooperate with vessels from other countries, thereby allowing it to evaluate the capabilities and performances of the navies of these countries," he told the Post.
Hsieh said the deployment could help the PLA survey the underwater and hydrological conditions in the region, and help improve its battle strategies.
China's move to deploy the nuclear submarine in the piracy operations came to light when it was docked at Colombo harbour twice last year, prompting India to raise red flags to the then Mahinda Rajapaksa regime which also permitted USD 1.5 billion Colombo Port City project to be developed by a Chinese firm.
The new Sirisena government which suspended the project for a review also decided not to permit the submarines.
A decision in this regard was conveyed by Sri Lanka's Foreign Minister Mangala Samaraweera when he visited Beijing in February this year.
Other analysts said the deployment was strategically significant, particularly because the region is seen as India's backyard.
“Someone may argue that sending a submarine, especially a nuclear one, for an escort mission is not as efficient as [sending other] military vessels, but it is a good opportunity for the People's Liberation Army to test the reach of the vessel,” Ni Lexiong, a Shanghai-based military commentator said.
It was necessary for the PLA to undertake such missions to train personnel and test vessel performance, he said.
Antony Wong Dong, a Macau-based analyst, expected China would send more military vessels to the Gulf of Aden, especially as the country's engagement overseas would be boosted under the “One Belt, One Road” initiative.
“China has to step up the protection of its interests abroad. Sending more military vessels (overseas) is essential to that aim,” he said.