Chinese authorities said they are taking a tough stance against illegal fishing by both domestic and foreign vessels in stretches of the nation's coastal waters, as the annual summer fishing moratorium got underway on Monday, lasting through mid-August in most areas.

The ban will be observed in parts of the north, east and south to conserve marine fish stocks, the Ministry of Agriculture and Rural Affairs said on its website.

It describes the ban as the country's most influential marine fish conservation effort, and said that regions subject to the ban include the Bohai Sea, the Yellow Sea, the East China Sea and the waters north of 12 degrees north in the South China Sea.

On Monday, the ministry also launched a law-enforcement operation in conjunction with the Ministry of Public Security and China Coast Guard in the waters off the coast of Shandong and Fujian provinces, and the Guangxi Zhuang autonomous region.

Liu Tianrong, deputy director of China Coast Guard's South China Sea division, said on Monday that his administration will step up patrols, adopt tough measures against foreign vessels violating the ban, and protect China's sovereignty and marine interests.

"We will abide by the law and take legal action," he said at a conference in Guangxi, whose coastline is in the Beibu Gulf in the South China Sea.

China has imposed the annual ban in the South China Sea since 1999, as part of efforts to promote the sustainable development of marine fishing and to improve the marine ecology.

For three days starting on Tuesday, China Coast Guard's South China Sea division and local authorities will patrol major fishing grounds and ports to ensure that the ban is observed.

Midway through the moratorium, three enforcement actions will take place in the Beibu Gulf, the Pearl River Estuary and along the marine border between Fujian and Guangdong provinces, in a bid to crack down on illegal fishing and protect marine resources.

The ban will end on Sept 1 for the Yellow Sea and the Bohai Sea north of 35 degrees north, but will last until Sept 16 in the East China Sea depending on certain fishing nets used.

According to authorities in Qingdao, Shandong province, the ban affects 17,000 fishermen. For the first time, the city will hand out marine conservation subsidies of some 70 million yuan ($10.6 million).

Zhejiang province's Agriculture and Rural Affairs Department said that after May 8, it will ban the sale of eight species of frozen or living catch, including hairtail, yellow croaker and pomfret.

Official data showed that authorities caught nearly 8,000 illegal fishing vessels in 2021.

Xinhua contributed to this story.