Australian police claim to have smashed an international drug syndicate in the country's biggest city Sydney.

Police said on Tuesday that they seized half a tonne of illicit drugs worth up to 525 million U.S. dollars, and arrested seven alleged smugglers.

They seized 206 kilos of crystal methamphetamine and 252 kilos of heroin - it's the largest seizure of crystal meth and the third largest heroin seizure in Australian Federal Police history.

Four of those arrested are from Hong Kong, and three are Australian nationals.

(SOUNDBITE) (English) AUSTRALIAN FEDERAL POLICE DEPUTY COMMISSIONER, ANDREW COLVIN, SAYING:

"We are confident that we have got the people responsible for this importation. It's easy to say the 'Mr. Bigs'. At the end of the day there's a lot of 'Mr. Mediums' and 'Mr. Littles' that work with 'Mr. Big'. I think we've got a good combination of the people responsible for this importation."

The seizure comes a year after police began investigating the drug syndicate after receiving tips from the United States Drug Enforcement Administration.

The contraband was found hidden in terracotta pots arriving on ships in Sydney.

Travis Brecher, Reuters