Investing.com -- Nokia Corp ADR (NYSE: NOK) shares dropped 4% in premarket trading Tuesday after the South China Morning Post reported the company plans to close almost all sites in mainland China by year end.

The Finnish telecoms equipment maker intends to cut most of its workforce in mainland China and close sites in stages by year end, according to sources cited by the South China Morning Post. The move would represent a retreat from China, which was once Nokia's largest single-country market globally.

The reported closures come as Nokia faces mounting pressure from domestic Chinese competitors in the telecommunications equipment sector. The company has operated in China for more than four decades.