Switzerland-based reinsurance giant Swiss re said Tuesday its chief executive was retiring, and posted a 31-percent hike in net profit in 2015 as the costs linked to natural disasters slid.

Swiss Re said its chief executive Michel Lies, 62, was set to retire after 35 years in the company and would be replaced on July 1 by the 46-year-old head of the company's reinsurance unit, Swiss citizen Christian Mumenthaler.

The change at the top was announced as the company, the world's second largest re-insurer, jubilantly announced strong results for 2015, as well as a planned new share buy-back of up to 1.0 billion Swiss francs ($1.0 billion, 911 million euros).

For 2015, Swiss Re said it had raked in a net profit of $4.6 billion (4.2 billion euros), boosted by lower costs linked to natural disasters.

Premiums however ticked in at $30.2 billion -- a full billion less than a year earlier, the company said, blaming mainly the negative impact of shifting exchange rates.

Not counting currency fluctuations, it said its income from premiums was up four percent last year.

Lies hailed the company's performance in 2015 as the culmination of several years of strong results.

"We have delivered a strong performance based on our underwriting discipline over the past five years and end this period with one of our highest-ever profits," he said in the earnings report.

Citing its "strong business performance and the very strong capital position", Swiss Re said it aimed to hike the dividend it pays to shareholders by 8.2 percent to 4.60 Swiss francs per share.

Following the announcement, Swiss Re meanwhile saw its share price dip 1.18 percent to 92.35 Swiss francs a piece in mid-morning trading, as the Swiss stock exchange's main SMI index was down 0.70 percent.