THREE Nigerian nationals suspected  of attempting to smuggle nearly a kilogramme of heroin through Phnom Penh International Airport by hiding it in giant clothes buttons were sent to the Phnom Penh Municipal Court on Sunday and Monday for further investigation,  Dangkor district police Chief Born Sam Ath said.  

The men, thought by authorities to be the masterminds behind a major drugs smuggling ring, are under interrogation by prosecutors, he added.

The trio were among 23 Nigerians arrested on Wednesday in a crackdown on drugs trafficking.

The other 20 men have been sent to the Department of Immigration for further investigation, Born Sam Ath said.

"We are now actively hunting to arrest more Nigerian suspects who we believe are hiding in Phnom Penh," he added.

Nearby Myanmar is the world's second-leading producer of heroin, and with its porous borders, Cambodia has increasingly become part of transit route for drug smugglers, police say.