In a report they released at a conference on Tuesday, Vietnam's Ministry of Public Security and Cambodia's Ministry of Women's Affairs said surrogacy trafficking gangs find Vietnamese women and take them to Cambodia to impregnate.

When their pregnancy is confirmed, the women are brought back to Vietnam and taken care of, and later taken to China for delivery.

Many women are also trafficked to do sex work.

The smuggling of the women has been most rampant at Moc Bai border gate in Tay Ninh Province in southern Vietnam.

Both governments have promised to fight human trafficking in the border region.

There would also be trilateral co-operation with China to strengthen the fight against trafficking, officials said.

Of over 3,400 Vietnamese trafficked since 2013, over 90 percent have been women, children or ethnic minorities.

Surrogacy is illegal in China, and Vietnam only allows it to be conducted for free for humane purposes and between family members.

Cambodia banned surrogacy in 2016 and has charged dozens of surrogates since, and they face up to 20 years in jail.

In April 2019, 11 surrogates were released on bail on condition they would raise the babies themselves under the supervision of courts.