The owner of Russia's third largest wireless operator Beeline, VimpelCom confirmed having an "unsubstantial" volume of Gemalto's SIM cards, but sought to alleviate fears of compromised privacy.
"Our technical experts consider the threat facing our clients' security highly unlikely… We have sent a corresponding request to Gemalto to remove all possible suspicions and fears," Anna Aibasheva, head of VimpelCom's press service, told RIA Novosti.
Russia's second largest mobile phone operator MegaFon echoed VimpelCom's comments that customers have nothing to worry about.
"The SIM card maker is conducting an internal investigation at the moment. In any case, all the mobile equipment purchased by MegaFon is certified, highly secure and provides strong encryption protocols," Tatyana Zvereva, the provider's spokeswoman, was quoted as saying.
"But one should understand that stealing SIM cards' encryption keys does not offer a direct opportunity to tap someone's phone… Eavesdropping on government officials' private conversations is unlikely to happen," Murtazin stressed.
Gemalto produces around two billion SIM cards a year, used by telecommunication giants including the United States' AT&T, T-Mobile and Verizon.
As of 2010, the most recent year when data was available, China accounted for nearly half of the chipmaker's global sales.
The latest disclosures are part of 1.7 million classified documents leaked in 2013 by former NSA contractor Edward Snowden, causing a US mass surveillance scandal.
