Currency volatility, higher catastrophe losses and ongoing energy market pressures factored into a 35% decline in second-quarter net income, insurer Liberty Mutual Holding Co. reported Wednesday.

Aside from net income of $254 million for the quarter, Liberty Mutual said its net written premiums increased 5.9% to $9.73 billion while revenue increased 4.3% to $10.38 billion.

Including catastrophes and prior year net incurred losses, Liberty Mutual said its second-quarter combined ratio climbed 2.1 percentage points to 102.4%.

“Things got a bit messy in Q2,” David Long, chairman and CEO of Boston-based Liberty Mutual Insurance, said Wednesday during an earnings conference call.

The main loss driver was the Venezuela devaluation and foreign exchange “under hyperinflationary accounting” resulting from changes by the Venezuelan government imposed in February on its foreign exchange controls, which led to a pretax loss of $81 million in the second quarter this year versus a pretax gain of $92 million in the same period last year, according to the earnings statement.

“The situation in Venezuela continues to deteriorate” and in light of the economic and political conditions, Liberty Mutual could make operational changes that include switching to another exchange rate or deconsolidating its operations in Venezuela, Dennis Langwell, executive vice president and chief financial officer, said during the conference call.

Catastrophe losses increased 19% in the second quarter to $800 million and rose 12% during the first half of the year to total $1.3 billion, Mr. Long said.

The losses include severe storms in the U.S. and New South Wales; floods in the U.K., Ireland and Chile; Hailstorm Ela; and Cyclone Niklas, Liberty Mutual said.

“We'll continue on the same path of profitable growth despite some bumps in the road such as we've seen in the second quarter of 2015,” Mr. Long said.

A depressed energy sector generated a pretax loss of $114 million in the second quarter and a $218 million pretax loss year-to-date, Mr. Langwell said.

For the first half of the year, the insurer's net income fell 19.2% to $530 million compared to the same period last year. Net written premiums increased 6.4% to $19.13 billion, while revenue increased 2.3% compared with a year earlier to $20.06 billion.

Its first-half combined ratio improved one-tenth of a percentage point to 99.8%, due in large part to a one-time, $91 million reduction in estimated prior year liability for state assessments related to workers compensation.