BEIJING (AFP) - Chinese police have broken up a cross-border drug-trafficking ring in raids that seized more than 400kg of cocaine - the country's biggest seizure in recent years, authorities said.

Nine suspects, including five from Hong Kong, were detained over the course of the operation, public security authorities in the southern province of Guangdong said in a statement.

Under Chinese criminal law they could face execution. Chinese courts have a near-100 per-cent conviction rate and the death penalty can be imposed for smuggling, selling, transporting or manufacturing more than 1kg of opium, 50g of heroin or methamphetamine, or a "relatively large amount" of other drugs.

A total of 400.5 kg of cocaine was seized, a "record amount" for a single case anywhere in the country in recent years, the police statement said on Monday.

"A cross-border drug transportation, stocking and distributing chain controlled by Hong Kong drug traffickers was busted," it said.

It gave no estimate for the drug's street value, but the official China Daily newspaper cited provincial drug enforcement chief Deng Jianwei as saying it was worth more than 334 million yuan (S$69.4 million).

Deng said the cocaine was shipped from South America. "Foreign traffickers are using Guangdong, which has advanced transportation networks, as a major transit centre to distribute drugs to other nations and regions," he said.