The ministry said the ban is "invalid" and directed provinces and cities to encourage fishermen to continue with their activities within Vietnam's territorial waters. They should also guide groups and teams to support fishermen at sea, it said in a statement.

The East Sea is internationally known as the South China Sea.

The ministry said fishing vessels with licenses valid until the end of this year can fish in the Tonkin Gulf common fishing area, but asked them to avoid the area east of the Tonkin Gulf delimitation line.

The ministry has also requested local authorities to strengthen the management and supervision of fishing activities and monitor fishing vessels' departure actively during this period, adding that the hotline of the Department of Fisheries Control will be available for emergencies.

On April 30, the Hainan Provincial Department of Agriculture announced that China’s annual fishing ban on the South China Sea has begun on May 1 and would last until August 16, Chinese news agency Xinhua reported, citing the South China Sea branch of the China Coast Guard.

The ban would apply to certain sea areas of the South China Sea that encompass parts of the Gulf of Tonkin and Vietnam’s Hoang Sa (Paracel) Islands.

No fishing activities are allowed in sea areas under China’s sovereignty within the time period, except in certain cases, according to the Hainan department. During the ban, China would perform safety checks for fishing equipment and vessels, as well as instruct its fisherpeople on relevant policies and skills, it said.

The Vietnam Fisheries Society has opposed China’s unilateral decision, saying the fishing ban has no legal value over sea areas under Vietnam’s sovereignty.

Four days later, Vietnam's Foreign Ministry also expressed clear opposition and asked Beijing not to complicate the situation further. Vietnam has full legal basis and historical evidence to assert its sovereignty over the Hoang Sa (Paracel) and Truong Sa (Spratly) Islands, as well as its legal rights over its waters in accordance with the United Nations Convention on the Law of the Sea (UNCLOS), Foreign Ministry spokeswoman Le Thi Thu Hang said.

China has been issuing similar fishing bans every year in recent times and Vietnam has consistently condemned and rejected them. China claims the bans seek to promote sustainable fisheries development and improve marine ecology.

China had seized the Paracel Islands from South Vietnam by force in 1974, and has been illegally occupying it since.

In 2012 it established the so-called Sansha City with the archipelago's Woody Island as its seat. The "city" also covers a number of reefs in the Spratly Islands that China seized by force in 1988 as well as the Scarborough Shoal.