* Cyprus issued passports to members of Cambodian elite
* Cypriot investigation to review eight cases
* Opposition say issue is 'stain' on the country (Adds opposition comment)
ATHENS, Oct 23 (Reuters) - Cyprus said on Wednesday it would investigate the circumstances under which relatives of Cambodia's prime minister were granted citizenship and did not rule out revoking passports if necessary.
A Reuters investigation published last week revealed that family members and allies of long-time Prime Minister Hun Sen have overseas assets worth tens of millions of dollars, and have used their wealth to buy foreign citizenship - a practice Hun Sen has decried as unpatriotic.
The Cypriot probe, announced by government spokesman Prodromos Prodromou, would review citizenship granted to eight relatives and persons close to Hun Sen.
"An investigation will take place for these cases, and if anything untoward is established decisions will be taken, not excluding revoking citizenship, if that is warranted," Prodromou told journalists after a cabinet meeting.
Cyprus has had a citizenship for investment plan in place since 2013, under which a minimum 2-million-euro ($2.2 million) investment can buy a passport and visa-free travel throughout the European Union. It has been reviewed and criteria are now stricter, authorities say.
Eight relatives or allies of Hun Sen - including Cambodia's police chief, who has been instrumental in clamping down on dissent, and its finance minister - sought Cypriot citizenship in 2016 and 2017, Reuters reporting showed.
One relative obtained citizenship because she was deemed "financially dependent" on her mother, only months after spending £5.5 million on a London apartment.
Hun Sen had previously denied claims from the opposition that members of his inner circle had passports from other countries and lived the high life overseas.
Reuters' disclosures triggered demands from Cypriot opposition parties for answers from authorities, with the AKEL main opposition party last week questioning how passports could be given to individuals "who probably couldn't find Cyprus on the map".
The probe triggered further indignation from the opposition on how the government could investigate itself objectively.
"Cyprus became an international laughing stock and no investigation will remove the stain from our island," the Greens and Citizens Alliance said in a statement.
AKEL said: "Do they feel any shame or responsibility for the international embarrassment of the country?"
The Cypriot government has repeatedly declined to comment on individual cases, citing data protection laws. Cypriot media had cited sources saying there was no question of revoking citizenship.
In his comments on Wednesday, Prodromou said naturalisations which had been the subject of recent media reports "had been given based on regulations of the past before today's stricter controls and limitations were enforced".
In the five years between the inception of the citizenship scheme and 2018, the Cypriot government approved 1,864 citizenship applications. Including family members, the number was more than 3,200.
The European Commission warned in a January report that what it called "golden passports" could help organised crime groups infiltrate Europe and raised the risk of money laundering, corruption and tax evasion.
($1 = 0.8996 euros) (Reporting by Michele Kambas Editing by Nick Tattersall)