Petrobras oil platforms at Campos basin in Rio de Janeiro. Picture: REUTERS
Picture: REUTERS

HANOI — Vietnam has warned China not to drill for oil after Beijing moved a giant rig at the centre of a previous maritime standoff back into disputed waters.

The move comes a day before a crucial political transition begins in Hanoi as the communist leadership meets for its five-yearly congress.

China has moved the HY-981 rig into an "overlapping area of continental shelves between Vietnam’s central coast and China’s Hainan island", Hanoi’s foreign ministry spokesman Le Hai Binh said late on Tuesday.

Hanoi closely monitors the movements of the oil rig, which caused a high seas standoff and deadly anti-China riots in 2014 after it was deployed for several months in waters claimed by Vietnam.

The oil rig’s move comes at a delicate time for Hanoi, with Vietnam’s ruling communist party preparing for a leadership change at the upcoming party congress, which starts on Thursday.

"Vietnam asked China not to proceed with drilling activities and withdraw the oil rig out of the area," Mr Binh said.

Hanoi and Beijing frequently trade diplomatic barbs over disputed island chains and waters in the South China Sea.

The leadership’s handling of its delicate relationship with China — which is the country’s largest trading partner — is a frequent flashpoint for domestic criticism of Vietnam’s authoritarian government.

Tension between the two communist neighbours has been rising in recent weeks over Chinese flights through Vietnamese airspace to the disputed Fiery Cross Reef in the Spratly Island group.

Vietnam accused China of threatening regional safety with the "unannounced" flights, while China ignored the warnings and hit back, arguing it had the right to conduct "state aviation activities".

China moved the HY-981 oil rig into contested waters in 2014, triggering protests and riots in Vietnam that left at least three people dead. China asserts ownership over virtually all of the South China Sea, putting it at odds with regional neighbours the Philippines, Vietnam, Malaysia, Brunei and Taiwan, which stake partial claims.