BUCHAREST, Jan 15 (Reuters) - Romania's energy ministry said on Wednesday it has notified a government agency that reviews foreign investment about potential national security risks stemming from a planned sale of E.ON's EONGn.DE local energy provider to Hungary's MVM.

E.ON announced the deal in December, which is subject to approval from Romanian authorities. MVM gets most of its gas from Russia, unlike energy providers in most European countries, and Romania's ministry has said previously that the sale could be blocked on security grounds.

E.ON Energie Romania is one of the European Union member's biggest gas and electricity providers, serving around 3.4 million customers.

The Commission to examine foreign direct investment (CEISD) is tasked with analyzing and approving foreign direct and new investment while ensuring national security is untouched.

The ministry said it has notified the commission about MVM's ties with Russia, saying it identified elements of "decisive influence, shadow control, influence by economic dependence and effective control."

It also said the sale contract left open the possibility that the Romanian energy provider could be sold later to an entity outside the European Union, which could facilitate the indirect transfer of control to economic or political entities that do not respect European legislation.

"We will act firmly and unequivocally to defend the national security of Romania and the energy security of the European Union which must rid itself definitively of its dependence on Russian gas," Energy Minister Sebastian Burduja said.

Spain last year vetoed a Hungarian bid for Madrid-based train maker Talgo TLGO.MC.

(Reporting by Luiza Ilie; Editing by Richard Chang)

((luiza.ilie@thomsonreuters.com; +4021 527 0312; https://www.reuters.com/journalists/luiza-ilie))