Law enforcement agencies have seized $1 billion of ice in the largest drug bust of liquid methamphetamine in Australia's history, federal Justice Minister Michael Keenan announced on Monday.

Three Hong Kong nationals and one Chinese national have been charged over their involvement in the drug syndicate, which is alleged to have imported 720 litres of methylamphetamine into NSW.

The syndicate was uncovered after border force officials at Sydney Airport notified the Australian Federal Police of a 33-year-old Hong Kong man, whom they identified as "high risk", as he entered Australia on November 9, 2015.

On December 26, Australian Border Force officials raided a shipping container from Hong Kong, which they believed was connected with the 33-year-old, and found a consignment of gel push-up bra inserts inside 86 boxes.