Surveillance drones hover over white-and-pink poppy fields in rural Pakistan, guiding men armed with assault rifles, weedicide sprayers and weed whackers — all part of a government operation to search out and destroy the farms that supply the key ingredient for opium and heroin.

Since Afghanistan’s Taliban rulers banned the lucrative crop three years ago, Pakistan has emerged as one of the world’s biggest suppliers of opium, with output increasing sharply this year as stockpiles decline.

Officials in the border province of Balochistan fear that ballooning cultivation could turn it into an opium production hub, fuelling addiction at home, damaging Pakistan’s reputation in Europe and enriching militant groups behind insurgencies that led to more than 2,000 deaths last year.