* H1 net falls to 58 billion yuan vs 68.7 bln year ago

* Takes 20.8 billion yuan loss on investments in China Fortune

* Gross written premiums fall 5% to 422.5 billion yuan

* Plans to repurchase 5-10 billion yuan worth of A shares

BEIJING, Aug 26 (Reuters) - Ping An Insurance Group Co of China , China's largest insurer by market value, reported a 15.5% fall in first-half net profit after a 20.8 billion yuan ($3.2 billion) loss suffered on investments in beleaguered developer China Fortune Land Development Co Ltd .

The results come after the insurer said in April it made 18.2 billion yuan of provisions for impairment losses on China Fortune, as it revealed a total 54 billion yuan exposure to the indebted property developer.

"Ping An made adjustments including impairment provisions, valuation adjustments, and other equity adjustments totalling 35.9 billion yuan to investments related to China Fortune in the first half of 2021," the insurer said in a filing to the Hong Kong stock exchange on Thursday.

Net profit fell to 58 billion yuan in the first half of 2021, compared with 68.7 billion a year earlier, with China Fortune exposure wiping 20.8 billion yuan off net profit, the insurer said.

The provision covered over 60% of Ping An's total exposure to China Fortune, said Yao Bo, executive vice president chief financial officer of Ping An, at a media conference.

Ping An "will assess whether to increase provisions in the second half according to the restructuring process of the developer," Yao added.

First-half earnings fell for a second consecutive year, having declined 29.7% in the first half of 2020, Reuters calculations showed.

"Ping An attaches great importance to investment risks caused by the debt crisis of China Fortune," said the insurer. The group's gross written premiums fell 5% to 422.5 billion yuan, while the number of retail customers rose 2.1% to 223 million.

Its banking unit Ping An Bank posted 28.5% growth in first-half net profit, with a non-performing loan ratio of 1.08% versus 1.10% a year-earlier.

Investors' confidence has been shaken in Ping An and its subsidiaries, with its Shanghai shares down by more than 40% year-to-date.

Some long-term investors and private fund managers cut their holdings in Ping An this year amid concerns over its large exposure to property firms and future profitability as the government tightened its grip over the real estate sector.

Ping An President Xie Yonglin said the market misunderstood the insurer's property investments.

"Property investment is a key part of our insurance investment portfolio," Xie told the press conference. "We're doing property investment to earn from the rental fees, instead of speculating on the land price."

To ease investors' concerns, the insurer also announced plans for a share buyback in its earnings report, boosting its share performance on Friday.

"As approved by the board of directors, Ping An plans to repurchase 5-10 billion yuan worth of A shares with proprietary funds," it said.

Ping An said it would divest and sell the assets it held in Founder Group, which is currently restructuring, other than its interest in the group's healthcare and core businesses.

($1 = 6.4810 Chinese yuan renminbi) (Reporting by Cheng Leng, Zhang Yan and Engen Tham; Editing by David Holmes and Stephen Coates)