Multinational human rights NGO Amnesty has named some of the top international companies for failing to respect human rights by using cobalt mined by child labourers in the Democratic Republic of Congo (DRC). Cobalt is used in lithium-ion rechargeable batteries of smartphones, cars and computers.

Apple Inc, Dell, HP Inc, Huawei, Lenovo (Motorola), LG, Microsoft Corporation, Samsung, Sony and Vodafone, as well as vehicle manufacturers like Daimler AG, Volkswagen and Chinese firm BYD, have been named in the report on human rights violations that takes place in artisanal cobalt mines in the DRC.

The DRC, one of the biggest suppliers of cobalt to the world, has a set of industrial and artisanal mines. The artisanal mines account for 20% of the DRC's cobalt supply and employ 110,000-150,000 people.

The artisanal mines employ children as young as seven. While the schoolgoing work before and after school hours, there are other children who can't afford an education and work full time in the mines.

Working hours in the mines can last up to 24 hours, a 14-year-old told researchers.

"I arrived in the morning and would leave the following morning," said 14-year old Paul, who had been working in underground tunnels since the age of 12.

"There is lots of dust, it is very easy to catch cold, and we hurt all over," said Dany, a 15-year-old boy.

The children who worked in the mines were paid 1,000-2,000 Congolese Francs per day (US$1-2).

A woman was reported as saying: "We all have problems with our lungs, and pain all over our bodies."

The report, which interviewed 90 people, also described a range of diseases, such as lung and skin infections, that ail those who work in the cobalt mines.

A 2012 UN report estimated children make up one-third of the total number of miners in the DRC.

The companies named in the report have also replied to Amnesty's accusations. 

Volkswagen has said: "The supply chain you (Amnesty) mapped out in your letter was refused by our supplier. To our best knowledge, the cobalt in our batteries does not originate from the DRC."

Microsoft said: "We have not traced the cobalt used in Microsoft products through our supply chain to the smelter level due to the complexity and resources required."