Yomiuri Shimbun says it has been provided with this information by “numerous sources within the Japanese government”. The Japanese government would be well-informed about this situation because some of its own warships have joined the task force led by Carl Vinson.
It is not unusual for the Russians and the Chinese to send spy ships to monitor the activities of the US navy, though because of the vastly enhanced means of surveillance possible today by satellites and by other means the days when the USSR was forced to maintain a vast fleet of spy ships consisting of converted trawlers to keep track of what the US navy was doing are long past. As Yomiuri Shimbun says
The dispatch of the intelligence-gathering vessels appears to be partly aimed at sending a warning signal to the United StatesI would add that what looks like the joint dispatch by the Chinese and the Russians of their spy ships to track the Carl Vinson and its accompanying escort ships is also a sign that the Chinese and the Russians are working together during this crisis, not just at the diplomatic level but at the level of their militaries as well.
It also reinforces the long-held impression that there is a secret agreement for intelligence sharing between them.
However the joint decision to dispatch spy ships to shadow the Carl Vinson and the rest of the US fleet would be a political one agreed by the two countries’ Presidents, Vladimir Putin and Xi Jinping.
President Trump’s National Security Adviser General McMaster has again said that China is “working” with the US on a “range of options” to solve the Korean crisis.
The dispatch of Chinese spy ships to the area alongside Russia’s is however the only practical action China has so far taken during this crisis. It suggests cooperation between Beijing and Moscow, not Beijing and Washington.