Travelers Cos., one of the largest property-casualty insurers in the U.S. reported that third-quarter profits rose more than four-fold.

Travelers Cos., based in St. Paul, Minn., said its third-quarter net income was $935 million or $1.65 per share, compared to $214 million or $0.36 per share in the prior-year quarter. Operating income was $914 million or $1.61 per share for the third-quarter ended September 30, 2009, compared to $330 million or $0.55 per share in the same quarter last year.

“We are pleased to report strong third quarter operating income of $914 million and operating return on equity of 14.1%,” said Jay Fishman, chairman and CEO of Travelers, in a statement. “These results were driven by underwriting profitability in each of our business segments and increased net investment income, as our non-fixed income portfolio yield improved to a positive level.”

Fishman added that the company remained “successssful in achieving positive renewal rate changes across all of our business segments, although net written premiums were down modestly, largely attributable to declining economic activity in recent quarters.”

Total revenue rose to $6.33 billion, an increase from the $6.15 billion reported last year. Its underwriting gain reached $338 million, after tax, an increase from the $208 reported last year. Net investment income, after tax, rose to $616 million, a $29 million jump from  last year.

The company reported net unrealized investment gains of $2.24 billion, a far cry from the net unrealized investment losses of $818 million for the third quarter last year.

Gross written premium fell, dropping to $5.94 billion from $6.13 billion a year ago, and net written premiums totaled $5.34 billion, down 3% from $5.48 billion for the same period last year.