With another act of maritime defiance against one of its South China Sea neighbors, the Chinese research vessel “Zhang Jian” has again entered the Philippines exclusive economic zone (EEZ) on Friday, Aug. 23. This latest intrusion comes just days after the Philippine government issued a warning that foreign ships will be met with an “unfriendly" response if they decide to pass through Philippine territorial waters.

MarineTraffic, a leading provider of ship tracking and maritime intelligence, provides real-time updates on the movements and locations of ships in harbors and ports. Their data shows that the Zhang Jian was off the coast of Samar at 3:15 a.m. early Friday. Samar is on the eastern side of the Philippine archipelago with its eastern shoreline on the Philippine Sea.

Previous Chinese infractions have occurred in the Philippines southern straits and on the eastern side of the country around the Spratly Islands. In some cases, Chinese vessels have rammed Philippine fishing boats causing them to capsize or they have simply turned off their automatic identification systems to avoid detection. Warships are required to give notice to the coastal authorities when they are in international waters.

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A senior Chinese military official said Saturday that the country will not “recklessly” use force in South China Sea. Pictured: Chinese coast guard vessel (left) followed by a Vietnamese coast guard ship near the area of China's oil drilling rig in disputed waters in the South China Sea, May 14, 2014. Getty Images/AFP/Hoang Dinh Nam

Twitter messages and Facebook screen shots helped to verify that the Zhang Jian is inside the Philippine EEZ. Analyst Ryan Martinson, assistant professor at China Maritime Studies Institute, posted a tweet indicating that this was the same vessel seen operating 80 nautical miles from the country's east coast in early August.

The track of the Zhang Jian was captured by Maritime law expert Jay Batongbacal, director of the University of the Philippines Institute for Maritime Affairs and Law of the Sea, who posted a screenshot from the Facebook group Karagatan Patrol. Batongbacal tweeted, "After hanging out for days outside the PH EEZ, Chinese research vessel quietly crosses and continues its survey into it, maybe thinking no one's looking.”

Philippine President Rodrigo Duterte issued warnings through his spokesperson Salvador Panelo who said Tuesday, “To avoid misunderstanding in the future, the president is putting on notice that beginning today , all foreign vessels passing our territorial waters must notify and get clearance from the proper government authority well in advance of the actual passage.”

Adding to the warnings was Foreign Affair Secretary Teodoro Locsin Jr. who called for a ban on foreign survey ships entering the country's waters. Loscin posted a Twitter message earlier this week that said, "To pick and choose invites suspicion of favoritism. Will universalize the ban. Period. Granting exception to one country will automatically lift ban universally.”