China Unicom, the second largest operator in the mainland, filed a profit warning with The Stock Exchange of Hong Kong and the US Securities and Exchange Commission, stating it expects its first half net profit to decline by about 80 per cent compared with the same period last year.

The decrease, it said, is mainly due to significantly higher selling and marketing expenses, the addition of tower usage fees, and higher energy charges and property rentals, which led to a substantial jump in network, operation and support expenses.

It noted in the filing that its first half operation was “on track as planned and its mobile business has achieved initial success in overcoming operational challenges”, adding 8.39 million mobile subscribers during the period, successfully turning around the downward trend in subscribers last year.

Its interim results for 2016 are scheduled to be announced on 17 August.

China Unicom, with nearly 261 million mobile subscribers, continues to lag in 4G. Market leader China Mobile had 480 million 4G users at the end of June, while China Telecom had 90 million. China Unicom added 28 million 4G subscribers in H1 to end June with 72.4 million.