TORONTO (Reuters) -Canadian insurer Manulife Financial shares fell by more than 3% on Thursday after it reported quarterly earnings below analysts' estimates, largely due to elevated credit and mortality losses in the United States. 

"This quarter, we did see variability, and it was negative variability," CFO Colin Simpson said in an interview after earnings were reported after the market close on Wednesday.

"We operate in the affluent and high net worth space and it's relatively by face amount, so that does potentially bring about variability in claims."

The U.S. business experienced an elevated number of claims on large policies under its life insurance segment, Simpson said, adding that it was normal claim volatility rather than an unfavorable mortality trend.

Core earnings at its U.S. segment fell 53%. The company earned core earnings of 95 Canadian cents for the second quarter ended June 30, two Canadian cents lower than analysts' estimates, according to data compiled by LSEG.

Manulife's Asia business performed better, boosted by new business. Its core earnings climbed 13% to $520 million in the quarter compared with the year-ago period.

Manulife's annual premium equivalent, a commonly used metric in the insurance industry to measure the total value of new business written in a given period, jumped 15% during the quarter, powered by a jump in its Asia unit.

Shares of Manulife have lost about 5% this year. They were down 3.5% on Thursday.

"That (the U.S. results) overshadowed what was otherwise a good result across the lifeco's other business lines, each of which reported core earnings that were slightly ahead of our estimates," Scotiabank analyst Mike Rizvanovic said in a note. 

Manulife, which has freed up billions of dollars in capital including through de-risking deals last year, said it would acquire 75% of private credit manager Comvest Credit Partners in a more than $1 billion deal to create a $18.4 billion private credit unit.

Paul Lorentz, global wealth and asset management head at Manulife, said in an interview there was an opportunity to use Manulife's scale in Asia to expand its platform in the region.   

Peer Sun Life Financial is set to report later on Thursday. Its shares have fallen about 1% so far this year.