Instead of buying RSA in a proposed transaction first announced in July, Zurich will focus on improving the performance of its general insurance business, it said in a statement.

With "recent deterioration in the trading performance in the Group’s general insurance business, Zurich...has terminated its discussions in connection with a possible offer for RSA," Zurich said. "The group’s focus instead will be on taking the necessary actions to deliver on the required performance."

Zurich announced aggregate losses of around $275 million from explosions at a container storage station in China. It said the final cost was uncertain.

The insurer also said recently completed reserve reviews indicate a likely negative impact of around $300 million in the third quarter for U.S. auto liability and other lines of business.

"Given the deterioration in profitability... General Insurance CEO Kristof Terryn is conducting an in-depth review of the business," Zurich said.

The insurer said it remains committed to achieving its financial targets for 2014 to 2016 of an after-tax return on equity from operating profit of between 12 percent and 14 percent.

In addition to claims relating to the Tianjin port explosions, Zurich said that it expects weaker-than-expected profitability in the general insurance business in the first half of 2015 to continue into the third quarter.

By John Miller

Stocks treated in this article : Zurich Insurance Group Ltd, RSA Insurance Group plc