Vietnam has again asked China to revise online maps that portray the Hoang Sa and Truong Sa Islands as part of Chinese territory.
The Vietnamese Foreign Ministry made the request on Wednesday afternoon, after arguing that the line encroaches into Vietnamese waters.
The request was inspired by the recent publication of official Chinese maps.
On January 18, the China National Bureau of Surveying and Mapping officially launched an online database called Map World.
The maps, which can be accessed at tianditu.cn and chinaonmap.cn, feature a dotted line that encircles the Hoang Sa (Paracel), Truong Sa (Spratly) islands with China's border.
Nguyen Phuong Nga, the spokesperson of the Foreign Ministry, argued that the images severely violate Vietnam's sovereignty over the islands.
Citing the UN's exclusive economic zone statue, Nga stated that the map encroaches into the 200 nautical mile sovereign border that extends into the East Sea from Vietnam's coastline.
"[The action] goes completely against regulations in the UN Convention on Sea Law (1982) and the spirit of the Conduct of Parties in the South China Sea (DOC)," Nga said. China and ASEAN member states signed the treaties in 2002.
"Vietnam objects to this action and asks that China immediately remove the wrong details from these maps."
Last May, Vietnam officially submitted a national report to the UN, asserting its sovereignty over the Hoang Sa and Truong Sa. In the report, Vietnam appealed to the 1982 UN Convention and agreements signed between the two nations.
Last November, Vietnam raised objections before the UN to China's inclusion of the islands on their maps. During the session, Vietnamese officials argued that China's claim was not grounded in any legal or historical foundation.