Hong Kong customs announced a record seizure on Friday of luxury goods that were headed to mainland China on a river barge in the latest operation to target an explosion of cross-border smuggling.

The haul included an array of highly sought-after items such as luxury watches, handbags, cosmetics and fins from endangered marine species.

Officials said the goods were worth about HK$1.2 billion ($154 million), by far the largest seizure made by the city's customs agents.

The operation took place on October 14 when customs discovered what they said was a suspicious vessel that claimed to be transporting plastic pellets.

Instead officers discovered a veritable department store of luxury items.

"The Chinese New Year is only around three months from now... so the mainland has a larger demand for these expensive foods like fish maw and sea cucumber than in normal days," customs investigator Cheng Tai-hei told reporters.

A 39-year-old woman and a 56-year-old man have been arrested in connection with the case.

Smuggling has been a mainstay of the triad organised crime gangs operating on both sides of the border for years but the phenomenon has surged during the coronavirus pandemic.

Police embarked on a crackdown after a marine officer was killed last month when her vessel was rammed by smugglers during a high-speed chase.

Customs investigators said syndicates have since turned to using other means, including river trade vessels, to smuggle goods to the mainland.

Simple economics makes the trade hugely lucrative.

Semi-autonomous Hong Kong has no sales tax, making it one of the cheapest places in the world to buy luxury goods.

But over in China, punitive taxes often mean luxury items cost up to double the price, providing a powerful smuggling incentive.

Cheng said the most expensive product seized in the bust were watches worth HK$600,000 each. In China, once tax is added, the same watches would cost HK$800,000, he added.

The raid also netted graphics cards that can be used for cryptocurrency mining, he said.