Global insurer Ace has booked a 15% increase in second-quarter net profit of $US746 million ($802 million), as the company benefitted from premium growth and a company acquisition.

Net profit climbed from $US649 million ($698 million) in the second quarter against the same period last year despite a marginally worse combined ratio of 87.8%.

Net written premium increased 17% to $US3.6 billion ($3.9 billion) while net investment income increased 13% to $US532 million ($572 million) during the quarter compared to the corresponding prior period. A 6% increase in underwriting profit of $US414 million ($445 million) also helped the final result.

However, half-year net profit declined 17% from $US1.35 billion ($1.45 billion) to $US1.12 billion ($1.2 billion).

Ace Chairman and CEO Evan Greenberg said the record operating performance was assisted by the acquisition of former Aon unit Combined Insurance.