LONDON, Aug 8 (Reuters) - The UK has launched a probe into a Britain-based unit of U.S. oil services company Halliburton Co.  in relation to the suspected payment of bribes to Nigerian officials, a source close to the matter said on Tuesday.

The probe by the UK's Serious Fraud Office (SFO) adds to investigations already under way in the United States, France and Nigeria into whether a consortium in which the unit, KBR, had a 25 percent stake made payments to secure construction work.

The SFO declined to confirm it was investigating KBR but said in an email: "The SFO is investigating allegations of illegal payments made to secure contracts in Nigeria. Searches were carried out in conjunction with City of London Police on 20 July 2006. The investigation continues."

Halliburton did not confirm the latest UK raids but said, in reference to the Nigerian consortium issue generally, that it was cooperating with various investigative agencies and was committed to getting a resolution to the issues.

"As this is an ongoing situation, it would not be appropriate to comment further at this time," company spokeswoman Melissa Norcross said in an email.

Halliburton said in a regulatory filing in March it had reason to believe that payments may have been made to Nigerian officials in relation to work on a liquefied natural gas terminal in Nigeria.

Halliburton said potential consequences of a criminal indictment arising out of these matters could include it being barred from U.S. government contracts.