Bermuda-based Arch Capital Group recorded a 70% increase in profit to $US595.7 million ($662.5 million) last year, driven by higher premiums and lower catastrophe losses.

It was lifted by the reinsurance division, which made a $US109.67 million ($121.78 million) fourth-quarter profit, compared with a loss in the corresponding period of 2012 after Superstorm Sandy.

Gross written premium (GWP) grew 8.5% to $US4.19 billion ($4.66 billion) for the year.

Underwriting income grew sharply across the group, rising more than 200% to $US451.73 million ($502.84 million) on a strong fourth quarter.

GWP from the insurance division increased 5% to $US2.71 billion ($3.84 billion) last year, while GWP from reinsurance gained 16% to $US1.48 billion ($1.653 billion).

In the reinsurance division, net written premium grew 36.1% to $US308.2 million ($342.9 million) on growth in casualty and other specialty lines.

The group’s combined operating ratio improved to 85.9% from 95.4%.