Four Chinese patrol ships returned to Jingha Port in southwest China's Yunnan Province on Friday after completing the 100th Mekong River joint patrol led by China, Laos, Myanmar and Thailand.

More than 200 law-enforcement officers and eight vessels from the four countries joined the mission that started on Tuesday, the latest edition of an ongoing operation that has boosted regional security over a period of years.

The monthly joint patrol was inaugurated in 2011 to conduct random inspections along the Mekong and crack down on drug trafficking, smuggling and other cross-border crimes in the region. The patrols have proceeded as usual this year despite the raging COVID-19 pandemic.

The Mekong River, known as the Lancang River along its Chinese stretch, meanders for over 4,900 km through China, Laos, Myanmar, Thailand, Cambodia and Vietnam before emptying into the sea. A key waterway for transnational shipping, the Mekong was, nevertheless, once a border area notorious for rampant criminal activities.

The river faced one of its darkest days on October 5, 2011 when a gang hijacked two cargo ships and killed 13 Chinese sailors in the waters near the Golden Triangle, an area known for drug production and trafficking.

The brutal incident sent shivers across the region and brought shipping activities in nearby waters to a halt.

Xiong Rui, a Chinese businessman who has been running a ship-building factory in Laos since 2001, said many ship-building companies along the river were then forced to suspend business.

China, Laos, Myanmar and Thailand issued a joint statement after the October incident, pledging to strengthen law-enforcement and security cooperation along the Mekong. In December 2011, the first joint patrol by the four countries was launched in an event marking the resumption of international shipping on the river.

Official data from the Yunnan provincial public security department showed the joint patrol teams have escorted more than 2,000 commercial ships and rescued 130 vessels in distress over the past nine years, preventing economic losses valued at up to 188 million yuan (about 28.7 million U.S. dollars). They have also seized over 4.6 tonnes of drugs during the patrols.

According to the department, the section of the Mekong between China's Guanlei Port and Thailand's Chiang Saen Port has not reported a single case of commercial ship hijacking since the joint patrols were launched. Major ports on the section have seen surging cargo throughput in the past nine years, and river cruises on the section had seen growing popularity before the pandemic.

Xiong said the Mekong has regained its former glory thanks to the joint patrols.

"Right after the patrols began, our company resumed production and commercial ships from the four countries started returning to the river," he said. "Now our company is getting orders for bigger ships that can transport more cargo."

Vidone Phutdavong, a Lao law-enforcement official, said during the 100th joint patrol that the patrols on the Mekong have brought safety and positive changes to the region.

He commended China's continuous support for the joint-patrol mechanism and hoped the four countries would further advance cooperation under the mechanism.

The COVID-19 pandemic has not hampered the joint patrols, but rather brought the four countries closer to safeguard the region and fight the pandemic together, said Yuan Yaping, with the water patrol general corps under the Yunnan provincial public security department.

Yuan said authorities in Laos and Myanmar donated medical supplies, including masks, disinfectants and protective gowns, to the Yunnan provincial public security department after the COVID-19 outbreak in China. Chinese law-enforcement authorities later returned the favor by donating supplies to their counterparts in Laos, Myanmar and Thailand.

In September, law-enforcement authorities from the four countries launched a joint operation targeting stowaways in a bid to stem the spread of COVID-19 in the region.

Zhao Kezhi, Chinese State Councilor and Minister of Public Security, said in a congratulatory letter to the 100th joint patrol team that he hoped law-enforcement authorities from the four countries would continue to strengthen cooperation in combating cross-border crimes and fighting the pandemic to better ensure regional stability and promote regional prosperity.