(Adds details on bribery allegations in China and other countries)
LONDON, May 27 (Reuters) - Britain's Serious Fraud Office (SFO) has launched a formal criminal investigation into GlaxoSmithKline Plc, posing a new challenge to the drugmaker, which already faces allegations of bribery in China and elsewhere.
Britain's biggest pharmaceuticals company said it had been informed on Tuesday that the SFO had "opened a formal criminal investigation into the group's commercial practices".
GSK said it would cooperate fully but gave no further details in a brief statement. A company spokesman declined to elaborate.
"GSK is committed to operating its business to the highest ethical standards," it added.
Chinese police said on May 14 they had charged the former British boss of GSK's China business and other colleagues with corruption, after a probe found the company used an elaborate scheme to bribe doctors and hospitals.
Authorities in China first accused GSK last July of funnelling up to 3 billion yuan ($480 million) in bribes to encourage doctors to use its medicines in a case that the company described in 2013 as "shameful".
Since then allegations have surfaced in other countries. GSK has said it is investigating claims that bribes were also paid to doctors in Poland, Iraq, Jordan and Lebanon.
($1 = 6.2486 Chinese Yuan)
(Reporting by Ben Hirschler and Andy Bruce, editing by David Milliken and David Evans)