British and Irish officials were checking on Tuesday whether two alleged members of a Russian spy ring used bogus passports from their countries as cover for espionage.
Documents filed at the US District Court for the southern district of New York accuse Richard Murphy and Tracey Lee Ann Foley of being deep-cover Russian agents charged with infiltrating US policymaking circles while posing as ordinary citizens. Murphy and Foley are alleged to have used a fake Irish and British passport respectively.
"We will be investigating this fully with the US," Britain's Foreign Office said in a terse statement. "It would be wrong to comment further at this stage."
Ireland's foreign ministry said it was seeking confirmation from the US embassy in Dublin.
The FBI announced on Monday the arrests of 10 alleged deep-cover Russian agents after tracking the suspects for years. They are accused of attempting to infiltrate US policymaking circles while posing as ordinary citizens.
An 11th person allegedly also involved in the Russian spy ring was arrested Tuesday in Cyprus.
In Britain, the US spy case has stirred memories of the country's own illegal Soviet spy - Melita Norwood, a civil servant who spent about 40 years passing atomic research and other secrets to Moscow. Authorities ruled against prosecuting the elderly grandmother when she was exposed in 1992. Norwood died in 2005 at the age of 93.
It is also reminiscent of the more recent scandal over the use of fake Irish and British passports in the assassination of a top Hamas militant in Dubai earlier this year.
Dubai police said Israeli agents posing mainly as European tourists were responsible for the slaying of Hamas official Mahmoud al-Mabhouh, who was found dead Jan. 20 in his hotel room. Dubai police say assassins using 32 fake passports _ including eight depicting fictional Irish citizens _ participated in the hit squad. Both the UK and Ireland expelled an Israeli diplomat each as a result, saying it was clear the Jewish state forged their passports as part of the assassination plot.
Israel has refused to confirm or deny its agents' involvement in the killing.