BEIJING, Jan. 2 -- The Chinese navy released on Wednesday the first photographs of what many military observers believe is the Liaoning aircraft carrier battle group as the nation's first aircraft carrier returned to its homeport of Qingdao, Shandong province.

The photos show the Liaoning sailing with several battleships, submarines and military aircraft performing a series of drills. The navy did not disclose when and where they were taken.

The carrier had successfully carried out 37 days of tests and training exercises in the South China Sea and returned to a People's Liberation Army's naval base in Qingdao, the navy said in a statement released on Wednesday.

"During the mission, the Liaoning conducted more than 100 drills and training exercises. The drills tested the structure's stress resistance, sailing speeds in deep water, navigational capabilities and weapons and equipment reliability," the statement said.

The Liaoning left Qingdao on Nov 26 and was anchored at a naval base in Sanya, Hainan province, three days later. On Dec 5, it set out on the training mission.

This is the carrier's first long-distance training voyage since it was commissioned in the PLA navy last year.

The carrier completed its first comprehensive combat training during the mission and performed a formation drill with other Chinese ships and submarines in the battle group, another first for the Chinese navy, the statement said.

Two missile destroyers, the Shenyang and Shijiazhuang, and two missile frigates, the Yantai and Weifang, participated in the mission. They escorted the carrier from Qingdao to Sanya. The use of four ships led military observers to speculate that the navy's carrier battle group has taken shape with the Liaoning as its core.