North Korean workers are being given a methamphetamine-based drug in the hope it will speed up a major construction project, according to reports.

Project managers in the city's capital of Pyongyang are said to be under so much pressure to finish the job on time that they have resorted to openly providing builders with the drug.

Nicknamed "ice," it is a form of the powerful stimulant methamphetamine, which is also known as crystal meth.