GlaxoSmithKline expects its financial performance in China to take a hit from Bejing's probe into bribery allegedly carried out by senior staff, the British pharmaceuticals company said on Wednesday.

"Clearly, we are likely to see some impact to our performance in China as a result of the current investigation, but it is too early to quantify the extent of this," GSK chief executive said in an earnings update.

Glaxo shares were down 11 pence of 0.65 percent at 12:17 pm as the FTSE 100 index gained 61.30 points or 0.93 percent to 6,658.74.