(Updates with details on portfolio valuation throughout, adds...

(Updates with details on portfolio valuation throughout, adds share moves in paragraph 5)

Dec 15 (Reuters) - Australian real estate company Dexus (DXS) said on Friday the book value of its portfolio declined by 5.2% for the six months to end-December, according to draft third-party independent valuations.

Dexus said independent valuations of 173 of its 176 assets resulted in a total estimated decline of about A$762.4 million ($510.50 million) from the prior book value at end-June.

The Australian real estate market, particularly office and retail, has been battling a downturn as home working and e-commerce constraints pressure valuations, with higher interest rates lowering building values and raising debt costs.

Analysts at Citi on Thursday warned that a potential decline in valuations could result in volatility in real estate stocks exposed to industrial and logistics assets. Citi remained "neutral" on Dexus with a price target of A$8.20.

Shares of the real estate company were trading marginally lower, as of 2348 GMT, after jumping as much as 1.6% earlier in the day to A$8.070, their highest level since mid-August.

Dexus in August sold an office building in downtown Sydney at a 16% discount to a 2022 valuation, and another premium office building in Sydney in June at a near 17% discount to independent valuation, reflecting price pressure on office spaces.

The firm's weighted average capitalisation rate - a metric to measure return on investment of real estate assets - across its portfolio expanded to 5.45% at December-end from 5.11% at June-end, Dexus said on Friday.

"We expect well-located quality assets to continue to outperform non-core locations and secondary assets," Dexus CEO Darren Steinberg said.

($1 = 1.4934 Australian dollars)