Zurich-based ACE Ltd. said its 2010 second-quarter profit increased 27 percent to $677 million compared with last year during the same time.

Chairman and Chief Executive Officer Evan G. Greenberg said the profit increase is due to the company’s successful risk management, diversification and underwriting.

ACE’s property and casualty underwriting income was $294 million compared with $355 million in 2009. Net written premiums were flat. Mr. Greenberg said slow economic recovery in the U.S., Europe and Japan, along with competition, impacted premium growth and will likely continue to do so “for some time.”

Net investment income rose 2 percent to $518 during the second quarter compared with the same time in 2009.