LONDON (Reuters) - British defence contractor Ultra Electronics (L:ULE) said the UK's Serious Fraud Office had opened a criminal investigation into "suspected corruption in the conduct of business" by it in Algeria.

Ultra said in a statement on Thursday that the SFO investigation concerned the business conduct of Ultra, its subsidiaries, employees and associated persons, and came after Ultra referred itself to the British fraud authorities.

"Given the stage of these matters, it is not possible to estimate reliably what effect the outcome of this matter may have on the group," Ultra said, adding that it continued to co-operate with the SFO.