The authorities in Pakistan have uncovered a drugs-smuggling ring that has shipped more than a-billion dollars worth of heroin out of the country over the last thirteen years.

A senior official said seven traffickers, operating from the international mail office in Karachi, had been arrested.

They'd posted more than three tonnes of heroin in envelopes and parcels, destined to European and African countries.

The operation was uncovered during wider government attempts to curb drug trafficking, including the destruction of opium poppy fields near the border with Afghanistan.