Chinese authorities released photos Saturday of armed Chinese naval aircraft training over disputed territory in the South China Sea, the South China Morning Post reported Sunday. The training maneuvers came just days after a United States naval ship sailed by in the region, amid heightening tensions over land claims from multiple Southeast Asian nations.

The armed jets that flew training missions took off from China's recently constructed airstrip on the Spratly Islands, the South China Morning Post reported. 

News of China's aircraft training in the South China Sea came several days after the U.S. sailed through part of the sea that China claims as its own and which the U.S. recognizes as international waters. 

"Both the defense ministry and foreign ministry have said China would have answers when its sea rights were breached. Such statements need to be followed by real actions," retired Chinese Gen. Xu Guangyu told the South China Morning Post Sunday.

The controversy centers around a swath of territory in the South China Sea that contains the Spratly Islands, a series of some 750 small, mostly uninhabited spits of land. The islands may be practically deserted, though they sit in the middle of several lucrative trade routes. They are virtually unexplored and could contain valuable oil or minerals.

Several countries in the region have made claims of sovereignty over parts of the territory, including Malaysia, the Philippines and Brunei. China has made the largest claim and has looked to reinforce that claim by covertly building artificial islands in the region.

News of China's latest activity in the South China Sea came as China, South Korea and Japan attended an economic conference in Seoul to discuss increased cooperation among the three regional allies. Japan was expected to lobby on behalf of the U.S. in the naval dispute while South Korea became increasingly caught in the middle. 

"We agreed to expand economic and social cooperation for the mutual prosperity of Northeast Asia, and also to strengthen cooperation among the three countries to create new growth momentum," South Korean President Park Geun-hye said after the summit Sunday, as reported by Reuters.