BEIJING, China — Shares in JD.com, China's second largest e-commerce firm, slid on Thursday after the company's revenues fell short of analysts' estimates in the second quarter following a worse-than-expected sale season.

The firm, which is part-owned by Chinese technology giant Tencent Holdings Ltd and US retailer Walmart Inc, posted a 31.2 percent rise in revenue to 122.3 billion yuan ($17.73 billion) for the quarter ended June 30.

That was marginally below an average estimate of 122.7 billion yuan from 22 analysts polled by Thomson Reuters I/B/E/S.

The company has been investing heavily in new business lines in the hopes of taking key markets from Alibaba Group Holding Ltd, but the effort continues to weigh on JD.com's profit margin.

JD posted a net loss of 1.54 yuan per American depositary share, compared with a loss of 0.35 yuan a year earlier.

The company's US-listed stock fell 5.7 percent in pre-market trading on Thursday following the results and is down 21.9 percent since the start of the year, roughly in line with China's other top tech firms.

JD.com's sales volumes are seasonally high in the second quarter due to the company's mid-year sales event '618', but profits took a hit due to increased spending on marketing.

During the 618 event JD.com reported sales of 159 billion yuan, up 33 percent from a year earlier, which analysts say was slightly lower than expected due to crossovers with national holidays.

Competition in China's slowing e-commerce market continues to drag on the company's growth. JD.com's revenue grew 11 percent in the first half of 2018, down from 16 percent in 2017.

With the backing of Tencent and Walmart, JD.com is competing fiercely with Alibaba on logistics, finance and retail, targeting hefty investments in fin-tech, grocery and luxury goods in the last quarter.

By Akanksha Rana, Cate Cadell; editor: Shailesh Kuber and Jan Harvey