Chinese boats have begun joint anti-smuggling patrols with Laos, Myanmar and Thailand along the Mekong River.

The first flotilla of 10 escorted cargo ships left Guanlei Port in southwest China's Yunnan province after an official launch of the four-country patrol that protected the vessels through to arrival Sunday in Chiang Saen, a Thai province.

Police and security representatives from the four countries made a show of solidarity at the official launch in Guanlei. The move is an attempt to make commercial shipping safer along the Mekong as the river passes though the four countries before entering Cambodia and Vietnam.

The patrol marks the reopening of shipping since closure by the Chinese after 13 sailors were killed in an attack on a Chinese ship in Thai waters in October. Many of the bodies -- two of them women cooks -- had their hands tied or handcuffed behind their backs, were blindfolded with adhesive tape or had been shot.

Thai police said they arrested nine soldiers believed to have been involved in the killings.

The reopening of shipping also comes as Thai police said they arrested five men on suspicion of smuggling hundreds of thousands of methamphetamine pills on a local bus.

Around 30 officers and security personnel were on board the ships that left Guanlei, the Chinese state news agency Xinhua said.

Ye Chao, owner of the Chinese ship Baoshou, welcomed the patrols. "We're reassured by the government stepping in," he said.

"We don't have to trade at the risk of our lives any more. Those gangs were fully armed and we had nothing to defend ourselves. We speak their language, so we survived. But for those who don't, anything could happen," Ye said.

The killings of the Chinese sailors on board their vessel galvanized politicians in the four countries into forming the joint patrol force. China will take a lead role in helping to train and equip the police forces, Xinhua reported.

The 3,050-mile Mekong River -- called the Lancang River in China -- is the world's 10th longest river and an important commercial and agricultural asset to the countries through which it runs.

The river flows from its source is high in Tibet through China's Yunnan province, briefly marks the border between Myanmar and Laos, then intermittently between Laos and Thailand. It enters Cambodia and finally Vietnam, forming the Mekong Delta and emptying into the South China Sea.

The six counties have a history of cooperating on agricultural Mekong River issues.

Laos, Thailand, Cambodia and Vietnam set up the Mekong River Commission in 1995 to help manage flooding and agricultural issues in the river's massive flood plain, which encompasses most of Laos. China and Myanmar became "dialogue partners" of the MRC in 1996.

But the Mekong flows through the infamous Golden Triangle area of Thailand, Laos and Myanmar. The triangle is known for opium and heroin smuggling but also is increasingly known for an illicit trade in methamphetamines.

Many ships have been hijacked to quickly move millions of methamphetamine pills along the river as part of the transportation system that includes horse and donkey routes through mountains.

Thai police said three of the five men they arrested on the weekend had been traveling on a bus accompanied by several suitcases containing 1.7 million methamphetamine pills and around 65 pounds of crystal methamphetamine.

Police arrested two men who were waiting to receive the drugs and pay the couriers, a report in the Bangkok Post newspaper said.