By Shivangi Lahiri and Rajasik Mukherjee

(Reuters) -Australia's QBE Insurance posted a stronger-than-expected interim profit on Friday, driven by solid premium growth in its international and North American operations, along with lower-than-anticipated catastrophe claims.

QBE, Australia's biggest insurer by market value, posted an adjusted net profit after tax of $997 million for a six-month period ended June 30, up from $777 million last year and ahead of LSEG estimates of $839.4 million.

The insurer, which operates in 27 countries including the United States, delivered a resilient first-half performance despite analysts warning that rising claims related to natural catastrophe and global economic headwinds could pressure its bottom line.

The insurer said its gross written premiums grew 5.9% to $13.82 billion in the first half of fiscal 2025.

Its combined operating ratio (COR), a key metric that measures underwriting profitability, improved to 92.8% from 93.8% last year. A ratio below 100% means the insurer earned more in premiums than it paid out in claims.

QBE Insurance paid out $479 million in catastrophe-related claims, primarily due to wildfires in California and storms and flooding events in North America and Australia. The figure was lower than the $527 million it incurred last year.

Its net claims ratio decreased to 62.8% from 64.2% a year ago.

However, investors remain cautious about the sustainability of certain profit drivers, such as lower claims and inclusion of prior-year reserves, which was reflected in QBE's share performance during the session.

The insurer's shares closed 8.8% lower at A$21.39 apiece, their lowest level since early May.

Investors looked past QBE's headline numbers and raised concerns about the nature of the profit drivers, said Nathan Zaia, senior equity analyst, Morningstar.

"It is always hard to predict movements in claims half on half, always a risk. The first half tailwind of prior year reserve releases also might not occur in the second half."

The Sydney-based insurer also declared an interim dividend of 31 Australian cents per share, up from 24 Australian cents last year.

(Reporting by Shivangi Lahiri and Rajasik Mukherjee in Bengaluru; Editing by Tasim Zahid, Alan Barona and Sherry Jacob-Phillips)