Liberty Mutual Holding Co says profit grew 28% to $US766 million ($853.9 million) in the first half, while catastrophe losses fell sharply.

Revenue increased 5% to $US18.97 billion ($21.15 billion) and catastrophe losses were $US824 million ($918.56 million), down 22% on the corresponding period last year.

Liberty Mutual Insurance Chairman and CEO David Long says underwriting results improved, with the combined ratio falling 3.5 percentage points to 99.9%, reflecting disciplined underwriting and profitable growth.