China has moved the $1bn Haiyang Shiyou 981 oil rig back to the East Vietnam Sea, located 167km from the Vietnam coast to explore oil and gas again.
The semi-submersible rig is owned by China National Offshore Oil (CNOOC).
The oil platform, currently located in an area west-north-west of Vietnam's Hoang Sa archipelago and south of the mouth of the Gulf of Tonkin, is expected to carry out exploration activities from 25 June to 20 August.
As reported by Vietnamese newspapers, China is redeploying the rig off the coast of China's Hainan Island in waters where the country and Vietnam's exclusive economic zones (EEZs) overlap.
In 2014, China deployed the Haiyang Shiyou 981 in the EEZ, which led to the worst breakdown in relations between the two countries, following a border war that took place in the year 1979.
"Vietnam claims that the operation of the rig is in violation of its territorial waters."
Vietnam's state-controlled Tuoi Tre newspaper stated on its website that maritime authorities were monitoring the rig's placement.
The latest rig movement comes weeks ahead of the first visit by Vietnam's leader Nguyen Phu Trong to the US.
The visit of the general secretary of Vietnam's Communist Party is expected to increase strategic ties between Washington and Hanoi.
CNOOC previously said that the rig was drilling in the Andaman Sea off the coast of Myanmar earlier this year.
The rig started operations on 9 May 2012 in the South China Sea, but was moved near to the Paracel islands on 2 May 2014.
Vietnam claims that the operation of the rig is in violation of its territorial waters.
Image: The $1bn Haiyang Shiyou 981 oil rig is owned by China National Offshore Oil. Photo: courtesy of VOA.
