KUNMING - A Chinese commercial vessel was attacked on Saturday by unidentified gunmen in the Mekong River's deadly Golden Triangle region, known for its criminal activity.

The merchant boat Shengtai 11 was shot at by firearms from the Laotian side as it was returning from Chiang Saen Port in Thailand to Guanlei Port in Xishuangbanna of Southwest China's Yunnan province at about 7:10 pm on Saturday, a police officer from the Yunnan provincial border defense corps, who did not want to be identified, told China Daily on Sunday.

The attacked boat, which was carrying timber, immediately sought help after the gunfire, he said.

Laotian police went to the scene by land to find the suspects while a Chinese vessel containing about 200 police officers from both China and Laos was sent to the spot to deal with the case, according to the insider.

"The ship was stopped at a safe place 2 kilometers away from the scene when the rescuers arrived early Sunday," he said, adding that bullet holes could be seen on the windows, walls and doors of the vessel.

The five crewmembers on board were unhurt, he said.

"We saw bullets from the river bank shooting at us when we were driving the boat. Because it was evening, the bullets looked like fireballs," Hu Tanyu, captain of Shengtai 11, told China Central Television (CCTV).

Hu then shut off the engine and lights, according to the CCTV report.

International transport on the Mekong River fully restarted after law enforcement agencies from China, Laos, Myanmar and Thailand established a joint patrol on Dec 10 and cooperated to safeguard the safety of the river.

"Police in Laos are still searching for the gunmen," said the unidentified police officer. "The river has been safer after the joint patrols, but in order to provide a thoroughly safe environment, we'll increase the number of patrols in the future."

However, Dai Peng, dean of the criminal investigation department of the Chinese People's Public Security University, said he does not think increasing the frequency of patrols can solve such attacks once and for all.

The waterway along the Mekong River is always dangerous, so strengthening security in the four surrounding countries "may be the key to making the river safe," Dai said.

"In addition, rescue operations for the attacked ships are likely to be delayed because the number of cargo vessels is much higher than the number of ships used for patrol," he added.

Thirteen Chinese sailors aboard two cargo ships were shot dead by a group of gunmen on Oct 5 on a section of the Mekong River that forms the border of Thailand, Laos and Myanmar, while four Chinese cargo vessels and a Myanmar patrol boat were attacked on Jan 4 at Wan Pung Port in Myanmar.

Zhang Yan in Beijing and Guo Anfei in Yunnan contributed to this story.