China's second aircraft carrier, the Shandong, recently conducted a series of night exercises, as the warship is on its way to becoming combat-ready around-the-clock, analysts said on Tuesday.

Entry to several regions in the South China Sea is prohibited due to military exercises from Tuesday to January 7, and observers speculated the Shandong could be involved.

The Shandong recently underwent a series of test exercises in the Bohai Sea, focusing on training objectives including departing port at night, sailing through narrow water channels, maritime search and rescue and damage management, China Central Television (CCTV) reported on Monday.

It also strengthened training on aviation support and further boosted the training level of crew members under high-intensity logistics support, CCTV said.

The report showed scenes of the Shandong training at night to the public for the first time, military observers noted.

Night operations are crucial to any military unit, and many tactical and strategic opportunities and threats come at night, a Chinese military expert told the Global Times on Tuesday, requesting anonymity.

The night exercises show how quick the Shandong's progress is to gain round-the-clock combat capability, the expert said. "It won't be long before we see night fighter jet takeoff and landing exercises on the Shandong."

CCTV said that the night training was held in the Bohai Sea, and this means it likely took place before December 20, when the Shandong set out from Dalian Shipyard by the Bohai Sea, sailed through the Taiwan Straits and entered the South China Sea.

Senior Captain Liu Wensheng, a spokesperson for the People's Liberation Army (PLA) Navy, said at the time that the Shandong aircraft carrier group will conduct exercises in the South China Sea, which is a normal arrangement in accordance with its annual schedule. 

"The PLA Navy will continue to hold more operations like this based on training requirements," he said.

Foreign commercial satellite images and online photos taken by residents and travelers showed the Shandong arriving at a naval port in Sanya, South China's Hainan Province. Recent overseas reports also suggest China's first Type 075 amphibious assault ship is also in Sanya.

Sanya's maritime safety administration on Monday released three navigation restriction notices, prohibiting entry of other vessels into waters in the South China Sea south, southeast and southwest of Hainan island.

Military observers expect the Shandong, possibly also the Type 075 amphibious assault ship and other warships, to participate in the 10-day exercises.