Hanoi said the ship and its coastguard escort had stepped up as it entered Vietnam's exclusive economic zone. On Friday, Beijing's Haiyang Dizhi 8 made numerous crossings across disputed waters, according to Marine Traffic satellite tracking data. The South China Morning Post reports that at least two Coast Guard ships were seen maneuvering around a Singapore-flagged support boat on an oil block.
Vietnamese Foreign Ministry spokeswoman Le Thi Thu Hang said: "Chinese research vessel Haiyang Dizhi 8 and its escort ships continue and expand their operations in Vietnam's exclusive economic zone and continental shelf, seriously violating the sovereign rights of Vietnam ".
"Once again, Vietnam demands that China immediately cease its serious violations, remove all its ships from Vietnam's maritime zones and give up repeating similar violations."
Vietnam has a huge board with China.
China and Vietnam are embroiled in a bitter fight, with tensions rising since July.
The fight increased after the Chinese state inspector began following and working on the seabed of the South China Sea.
This is when Beijing begins deploying coastguard ships in the highly disputed South China Sea while trying to make itself visible to rivals.
Experts believe China's move is an attempt to assert its dominance in the region.
The Washington-based Asia-Pacific Maritime Transparency Initiative released a report stating that 14 vessels were identified as Chinese vessels.
"And if this strategy succeeds in Luconia and Second Thomas (as it probably did in Scarborough), it will serve as an attractive plan to extend the Chinese administration to other reefs and shoals."
He added: "This makes them ideal for operations that may involve threatening collisions and, if necessary, lead other vessels to clear them without lethal force."
Reports suggest that the ships are not armed.
They have water cannons and small arms, but are believed to be larger than their rivals in the South China Sea.
By ensuring that vessels are deployed, China may become a visible presence in places where it claims to have sovereignty, but in reality it has no permanent equipment there.
After the UK announced that it would send the new HMS Queen Elizabeth aircraft carrier to the volatile South China Sea region.
This followed France's announcement that it had sent its frigate, Dixmude, to the Spratly Islands, which are a contested group of islands within the Nine Dash Line.
China has responded to news from European nations ordering its fleet's main ships to sail to the disputed maritime area.
Maj. Gen. Su Guanghui, China's defense attaché to Britain said last week: "If the United States and the United Kingdom come together in a challenge or violate China's sovereignty and territorial integrity, that would be hostile action. "