HONG KONG (Reuters) -HSBC ( HSBC ) Chief Executive Noel Quinn will retire, it said on Tuesday, in a surprise departure from the bank that he has overhauled in the past five years through a sweeping series of asset sales across the globe.

The bank said has already launched a formal process to find a successor. Chief Financial Officer Georges Elhedery, appointed to the No. 2 role last January after a sabbatical before which he headed the bank's markets business, is likely the leading internal candidate for the job.

The bank also reported pretax profit that came in at $12.7 billion for the quarter ended March versus $12.9 billion a year earlier, as it struggles to cope with rising costs from expansion in Asia and amid inflationary pressures. The results were better than the $12.6 billion average of analysts' forecasts compiled by HSBC ( HSBC ).

The London-headquartered bank also announced $3 billion worth of share buybacks on top of $2 billion in share purchases announced in February.