Yandex is taking legal advice following a raid of its offices in Ukraine on Monday and accusations its employees passed personal data about Ukrainian users to the Russian special services.

"Two weeks ago, Ukraine sanctioned Yandex.Ukraine and Yandex LLC, subsidiaries of Yandex N.V. and blocked Ukrainian users from accessing our services and websites. Today, Ukrainian Security Service (SBU) conducted searches at Yandex offices in Kyiv and Odesa," the NASDAQ-traded Russian Internet company said in a statement.

"SBU is accusing management and employees of Yandex.Ukraine of gathering personal data of Ukrainian users and transmitting them to Russian security forces," Yandex said.

"Neither our employees in Ukraine nor management of Yandex.Ukraine have access to personal data of Yandex users. At Yandex, our users are central to everything we do and we have always fiercely protected our users' data privacy. We implement strong security measures across all of our services to ensure both the anonymity of users and the confidential transfer of sensitive data. All data is stored securely across Yandex data centers and the aforementioned investigation does not affect the security of user data," it said.

"In each country in which we operate, Yandex complies with strict legal procedures for information requests by local authorities, which provides that any requests may be considered only upon a proper court decision. The allegations that our employees were transmitting personal data to Russian security forces have no merit," Yandex, which has 17 offices worldwide, said.

Yandex said it was consulting with lawyers and "undertaking all appropriate measures to ensure the safety of our team, which is our highest priority."

"Yandex is a technology company that builds intelligent products and services powered by machine learning. Our goal is to help consumers and businesses better navigate the online and offline world. Since 1997, we have delivered world-class, locally relevant search and information services. Additionally, we have developed market-leading on-demand transportation services, navigation products, and other mobile applications for millions of consumers across the globe," Yandex said.