* Doctors allegedly offered free samples, travel benefits
* Follows earlier claims of bribes in China, Poland, Iraq (Adds details on allegations, further GSK comment)
LONDON, April 16 (Reuters) - GlaxoSmithKline, Britain's biggest drugmaker, said on Wednesday it was investigating allegations of bribery involving some of its staff in Jordan and Lebanon, following earlier claims of corruption in China, Poland and Iraq.
"GSK can confirm we are investigating allegations regarding the activity of a small number of individuals in our operations in Jordan and Lebanon," the company said in statement.
"We started investigating using internal and external teams as soon as we became aware of these claims. These investigations have not yet concluded."
GSK faces its biggest challenge over corruption allegations in China, where authorities in July accused it of funnelling up to 3 billion yuan ($483 million) to doctors and officials to encourage them to use its medicines in a case that rocked the pharmaceuticals industry.
This month its reputation was placed under a further cloud by claims of similar wrongdoing in Iraq and Poland. Poland's Central Anti-Corruption Bureau said on Monday that 13 people had been charged, although GSK said it had found evidence of misconduct by only a single Polish employee, who was disciplined.
The company said it did not have a systemic issue with unethical behaviour and said the 161 violations of its sales and marketing policies in 2013 was very similar to rates reported by other pharmaceutical companies.
GSK recently took steps to tighten up its marketing procedures, including a move to stop the practice of paying doctors to speak on its behalf and tying compensation of sales representatives to the number of prescriptions doctors write.
The latest allegations about Jordan and Lebanon were first reported in the Wall Street Journal, which cited emails from a person who first contacted GSK in December.
The emails alleged that GSK sales representatives bribed doctors to prescribe drugs and vaccines by issuing free samples to doctors that they were allowed to sell on.
GSK staff were also alleged to have permitted doctors to bring their spouses on paid-for business trips and speaking engagements that may not have taken place, according to the emails. (Reporting by Ben Hirschler; Editing by Greg Mahlich)