BEIJING (Reuters) - China’s navy has in recent days carried out more exercises in the disputed South China Sea, the Defence Ministry said on Sunday, calling them routine drills.

Chinese dredging vessels are purportedly seen in the waters around Mischief Reef in the disputed Spratly Islands in the South China Sea in this still image from video taken by a P-8A Poseidon surveillance aircraft provided by the United States Navy May 21, 2015. REUTERS/U.S. Navy/Handout via Reuters

China claims almost all of the energy-rich waters of the South China Sea, through which more than $5 trillion of maritime trade passes each year. The Philippines, Brunei, Vietnam, Malaysia and Taiwan have overlapping claims.

“The People’s Liberation Army Navy in recent days organized a fleet to go to relevant seas in the South China Sea, by way of the Western Pacific, to carry out exercises,” China’s Defence Ministry said in a brief statement.

“This action is a routine arrangement made in accordance with this year’s naval training plan,” it added, without elaborating.

Pictures on social media accounts of Chinese state media have in recent days shown pictures of Chinese navy ships engaged in live-fire exercises in the South China Sea, without saying where exactly they took place.

China periodically announces such exercises in the South China Sea, as it tries to demonstrate it is being transparent about its military deployments.

China has been at odds with the United States of late over the strategic waterway.

Washington has criticized Beijing’s building of artificial islands in the South China Sea’s disputed Spratly archipelago, and has conducted sea and air patrols near them.

Last month, U.S. B-52 bombers flew near some of China’s artificial islands and at the end of October a U.S. guided-missile destroyer sailed within 12 nautical miles of one of them.

China expressed concern last week about an agreement between the United States and Singapore to deploy a U.S. P8 Poseidon spy plane to the city state, saying the move was aimed at militarizing the region.