An American warship sailed as close as 8.5 nautical miles to Fiery Cross Reef – one of Beijing’s artificial islands in the South China Sea – in the US Navy’s first such operation this year, a Chinese think tank said. The USS Montgomery, a littoral combat warship, passed into an area near the reef, in the contested Spratly Islands, on Monday morning, according to the South China Sea Strategic Situation Probing Initiative. “The closest it got to Fiery Cross Reef was 8.5 nautical miles,” the think tank under Peking University said in a report on Wednesday, citing data from the warship’s automatic identification system. It said the warship had also sailed close to Johnson South Reef, which is also occupied by China. “Its activities close to Johnson South Reef could possibly be more complicated, and more provocative,” the think tank said, adding that the warship’s automatic identification system had been turned off well before it arrived there. The USS Montgomery has become a key part of US operations in the South China Sea since it was deployed to the Changi naval base in Singapore in July. The report said the warship had spent a day sailing from Changi to the Spratly Islands. It also noted that it was not unusual for a naval vessel to switch off its automatic identification system so as not to reveal a military operation. The Spratly Islands are located west of the Philippines and are subject to rival claims from China, Brunei, Malaysia, the Philippines, Taiwan and Vietnam. Explained: South China Sea dispute China’s military on Tuesday hit out at the US, saying the warship had made “deliberate provocations” . Senior Colonel Li Huamin, spokesman for the People’s Liberation Army’s Southern Theatre Command, said China had sent air and sea patrols to “track, monitor, verify and identify” the USS Montgomery when it sailed through the Spratlys. Li said the Southern Theatre Command would be on “high alert, and take all the necessary measures” to protect China’s sovereignty in response to the warship’s passage. The US Navy had “asserted navigational rights and freedoms in the Spratly Islands, consistent with international law” in its freedom of navigation operation, a spokesman told The Japan Times on Tuesday. The voyage “challenged the restrictions on innocent passage imposed by China, Vietnam and Taiwan”, said Lieutenant Joe Keiley, a spokesman for the 7th Fleet. In December, the think tank said the United States had held at least 85 joint military exercises with its allies in the Indo-Pacific region in 2019 as it sought to challenge Beijing’s rise. It said the drills between January and November had varied in size, but their aim was consistent – to extend America’s presence in the region and strengthen the defence capabilities of its allies. Of the joint and multinational exercises staged in that period, the Philippines was involved in at least 16, Thailand nine and Singapore six, the report said. It also said military cooperation between both Singapore and Thailand and the US was deepening, even though neither were involved in territorial disputes with Beijing in the South China Sea. Purchase the China AI Report 2020 brought to you by SCMP Research and enjoy a 20% discount (original price US$400). This 60-page all new intelligence report gives you first-hand insights and analysis into the latest industry developments and intelligence about China AI. Get exclusive access to our webinars for continuous learning, and interact with China AI executives in live Q&A. Offer valid until 31 March 2020.