LONDON -- Shell (IW 1000/1) on Thursday said in a surprise announcement that chief executive Peter Voser will retire next year, as it also posted falling first-quarter net profits on the back of lower crude oil prices.

"The board of Royal Dutch Shell plc today announced that Peter Voser... has elected to retire from the company in the first half of 2014," a statement issued by the Anglo-Dutch group said.

In a message to staff, Voser said he wanted to spend more time with his family, after more than 25 years working for Shell.

Voser, 54, has been chief executive since July 2009. Shell said it would review internal and external candidates to find a successor.

"After such an exciting executive career I feel it is time for a change in my lifestyle and I am looking forward to have more time available for my family and private life in the years to come," he wrote to colleagues.

Voser added that he would still maintain a "limited" number of non-executive roles at other companies.

The news was delivered alongside the announcement of a 6% drop in Shell's first-quarter net profits to $8.18 billion.

Earnings after tax in the three months to March compared with $8.7 billion in the same period of last year.

"Our industry continues to see significant energy price volatility as a result of economic and political developments," Voser said in the earnings release.

"Oil prices have fallen recently but Shell is implementing a long-term, competitive and innovative strategy against this volatile backdrop."

Shell said that its current cost of supplies -- which strips out gains or losses in the value of inventories -- rose four percent to $7.95 billion owing to higher refining margins.

Total oil and gas production meanwhile edged higher to 3.559 million barrels of oil equivalent per day in the reporting period, from 3.552 million in the same period of 2012.

Output was affected by security problems in Nigeria and divestments.

Copyright Agence France-Presse, 2013