The Defense Ministry said Tuesday that China’s sole operating aircraft carrier, the Liaoning, had passed through the Miyako Strait between the island of Miyako and Okinawa’s main island as it ventured into the Pacific that morning.

The Liaoning, which did not enter Japanese waters while traversing the 150-nautical-mile-wide strait, was accompanied by an apparent carrier task force group made up of five other vessels, including two guided-missile destroyers and two frigates, the ministry said in a statement.

It also said a combat support ship had joined the task force, the first time such a vessel had been sighted making the voyage.

The vessels were expected to hold drills in the Pacific, exercises that were likely to be intended to check military activities in the waters by the U.S., Japan and nearby Taiwan.

The passage of the Chinese carrier through the strait, a key strategic gateway into the Pacific for China, was the third confirmed instance since December 2016.

In April last year, the Defense Ministry said that China had for the first time conducted a drill in the Pacific with the Liaoning.

While the Liaoning, a refurbished Soviet vessel, is currently China’s only active carrier, the country’s first domestically produced carrier, the so-called Type 001A, has been conducting sea trials in recent months, according to Chinese state-run media. Analysts say that carrier will likely enter into service sometime this year.

Tokyo and Beijing are embroiled in a dispute over the Japanese-administered Senkaku Islands, known in China as the Diaoyu, in the East China Sea. China has sent vessels to the area around the islands for a record 61-straight days, as of Tuesday.

China is in the midst of a military modernization program heavily promoted by President Xi Jinping, who has overseen a shift in focus toward creating a more potent fighting force, including projects such as building a third aircraft carrier, integrating stealth fighters into its air force and fielding an array of advanced missiles that can strike air and sea targets from long distances.

This modernization push has also seen ramped-up military exercises by the air force and navy as China seeks to expand its reach further from its shores.