The Defense Ministry announced Friday that the Maritime Self-Defense Force's largest warship, the Izumo helicopter carrier, wrapped up three days of joint drills with the aircraft carrier USS Ronald Reagan in the disputed South China Sea.

The exercises, which ended Thursday and also saw the MSDF destroyer Sazanami take part, were an apparent show of naval force in the strategic waters. Beijing claims almost all of the South China Sea, where it has built up and militarized a string of man-made islands, stoking concern among regional claimants.

U.S. "freedom of navigation" patrols in the sea have angered Beijing as it seeks to reinforce effective control of much of the waters, through which $5 trillion in trade passes each year. The Philippines, Vietnam, Malaysia, Taiwan and Brunei also have overlapping claims.

China has also ramped up naval and air operations in the area, sending bombers and fighter jets on "combat patrols" that Beijing has called a "regular practice."

While Japan and the U.S. do not have any territorial disputes in the South China Sea, Tokyo is embroiled in a separate row with Beijing in the East China Sea over the Senkaku Islands, which are claimed as Diaoyu by China and Tiaoyutai by Taiwan.

The Izumo and Sazanami have taken part in multiple exercises with the U.S. military and others in the South China Sea since arriving in the area in early May. Earlier this month the MSDF helicopter carrier Hyuga and the destroyer Ashigara joined the Reagan and the aircraft carrier USS Carl Vinson for drills in the Sea of Japan.