GlaxoSmithKline faces new allegations of corruption, this time in Syria, where the drugmaker and its distributor have been accused of paying bribes to secure business, according to a whistleblower's email reviewed by Reuters.

Britain's biggest drugmaker said Thursday it was investigating the latest claims dating back to 2010 that were laid out in the email received by the company on July 18.

The allegations relate to its former consumer health care operations in Syria, which were closed down in 2012 due to the worsening civil war in the country.