KUNMING — Law-enforcement authorities from China, Laos, Myanmar and Thailand joined forces on Sept 21 for the 109th Mekong River joint patrol.

Three Chinese vessels departed on the morning of Sept 21 from Guanlei Port in Southwest China's Yunnan province for the four-day patrol, the Yunnan provincial public security bureau said.

During the patrol, the joint law-enforcement team will crack down on cross-border crimes, including illegal immigration, drug smuggling, and criminal activity related to telecommunication and internet in the Mekong River basin, said the bureau.

The Mekong, known as the Lancang in China, is a vital waterway for cross-border shipping.

China, Laos, Myanmar and Thailand have been carrying out joint patrols in the river since December 2011.