US insurance giants Liberty Mutual and Berkshire Hathaway made strong gains during the first quarter as rising revenues countered the cost of recent natural catastrophes.

Liberty Mutual recorded net profit of $US315 million ($351 million) during the period compared to just $US22 million ($24 million) at the same point a year ago.

Net written premium of $US7.2 billion ($8 billion) was up 2.6% and revenue climbed more than 10% to $US8.2 billion ($9.1 billion).

The combined ratio reflected tough underwriting conditions, increasing 2.7 percentage points to 102.2%.

“We turned in another solid quarter of growth and earnings despite natural catastrophes, a very competitive marketplace and continuing economic challenges,” CEO Edmund Kelly said.

Berkshire Hathaway has reported first-quarter net profit of $US3.6 billion ($4 billion) in a vast improvement on the $US1.5 billion ($1.7 billion) loss recorded during the opening quarter of last year.

The company, which is led by legendary US investor Warren Buffett, includes reinsurer Gen Re and major US insurer Geico. It reported a $US278 million ($309 million) impact from natural catastrophes including the Chilean earthquake and storm and weather-related losses in Australia, the US and Europe.

Operating earnings lifted 30% to $2.2 billion ($2.5 billion), including a 12% increase in underwriting earnings of $US226 million ($251 million).

Revenue from insurance and other related activities climbed 25% to $US25.6 billion ($28.5 billion).

The company says “extraordinary capital strength” remain a key marketing strategy for its insurance business.