Lured by jobs in Europe, Vietnamese migrants are smuggled illegally often through China or Russia, Carsten Moritz, head of the human trafficking unit of the Federal Criminal Police Office (BKA), told public broadcaster RBB Monday.
Arrivals from Vietnam frequently work under "exploitative conditions" to pay off smuggling debts, which cost around 10,000 to 20,000 euros ($12,000 to $24,000) per person.
A "huge network" that is "active all over Europe" is behind trafficking from Vietnam, according to the BKA, generating "enormous sums" for criminals.
A Europe-wide operation will be launched this year to tackle the problem initiated by the BKA and bringing in police from countries including Poland, Britain, the Netherlands, Austria, Switzerland, the Czech Republic and Belgium as well as EU law enforcement agency Europol.
Police have previously found migrants -- including minors -- illegally working in massage parlors, nail salons and restaurants, as well as the textile and cleaning industry.
The eastern Berlin district of Lichtenberg, home to the Dong Xuan Center, one of Germany's largest Asian markets, is of central importance, Moritz said.
In March last year, German police carried out a series of raids against suspected Vietnamese traffickers and arrested six in relation to charges of smuggling 155 Vietnamese people to Germany.
People who choose to make the perilous journey to Europe often endure appalling conditions.
In 2019, 39 Vietnamese migrants were found dead in a refrigerated truck in Britain shortly after it had crossed the Channel from mainland Europe.
The ringleader Gheorghe Nica was arrested in Frankfurt in January 2020 on a European Arrest Warrant and later convicted in London of 39 counts of manslaughter.
Another suspected leader in the smuggling, a 29-year-old nicknamed "the Bald Duke", was arrested in Germany in May, sources told AFP at the time.
There are around 188,000 people of Vietnamese descent in Germany, according to official statistics.
Many Vietnamese came as so-called guest workers to East Germany, staying after the fall of the Berlin Wall.
Others are descended from the "boat people" who arrived in West Germany after fleeing their homeland at the end of the Vietnam War.