GlaxoSmithKline (GSK) is facing new allegations of bribing doctors and officials in Syria to increase the sales of its medicines.

This fresh round of charges was reported by the Reuters news agency after an anonymous email was sent to chief executive Andrew Witty and GSK audit committee chair Judy Lewent.

The email stated: "GSK has been engaging in multiple corrupt and illegal practices in conducting its pharmaceutical business in Syria."

"All the claims in this email will be thoroughly investigated using internal and external resources as part of our ongoing investigation into operations in Syria."

GSK said that it will investigate the new claims. The company has suspended relations with its Syrian distributors as a result of the investigation.

A GlaxoSmithKline spokesman said: "All the claims in this email will be thoroughly investigated using internal and external resources as part of our ongoing investigation into operations in Syria.

"We are committed to taking any disciplinary actions resulting from the findings. We have suspended our relationship with our distributors in the country pending the outcome of our investigation."

GSK has also come under the scrutiny of US and UK regulators, with the US Department of Justice investigating possible violations of the Foreign Corrupt Practices Act (FCPA), while the UK’s Serious Fraud Office is set to probe into GSK’s overseas activities.

The drug maker has also faced similar bribery claims in China, Iraq, Jordan, Lebanon and Poland.

In Syria, GSK sales were less than £6m a year, compared to a group turnover of £26.5bn in 2013.