China officially launched its first domestically built aircraft carrier on wednessday.

It will be joining an existing one bought second-hand, amid rising tensions over North Korea and worries about Beijing's assertiveness in the South China Sea.

According to military experts, the carrier, designed in China and built in the northeast port of Dalian, is not expected to enter service until 2020, as it will take time to fully kit out and arm.

The launch had been well-flagged as foreign military analysts and Chinese media have for months published satellite images, photographs and news stories about the second carrier's development. China confirmed its existence in late 2015.

The launch follows China's celebration on Sunday of the 68th birthday of the founding of the Chinese navy, and comes amid renewed tensions between North Korea and the United States over Pyongyang's nuclear and missile programs.