Human rights watchdog Amnesty International has accused major technology companies including Apple, Samsung and Sony of using cobalt mined by child labourers in Congo. The NGO said that the companies are failing to do basic checks on the source of the materials used in their products.

An Amnesty report published on Tuesday traces the cobalt used in lithium-ion batteries that power electronic devices to mines where children as young as seven and adults "work in perilous conditions". The report documents how traders buy cobalt from areas where child labour is rife and sell it to Congo Dongfang Mining, a subsidiary of Chinese mineral giant Zhejiang Huayou Cobalt Ltd.

When contacted by Amnesty, the tech companies said they had a "zero tolerance policy" on child labour, reported The Independent. Apple said it took "any concerns seriously and [will] investigate every allegation". Sony said it was carrying out a "fact-finding" inquiry. Microsoft said it no longer sourced cobalt from a Chinese firm implicated in the Congo trade.

The Democratic Republic of Congo is said to produce about half of the world's cobalt. At least 80 artisanal miners died underground in southern Congo between September 2014 and December 2015 alone, said the NGO.