MOSCOW (Reuters) -Russia's largest oil producer Rosneft acquired Tomtor, country's largest rare earth metal deposit, a companies registry showed on Wednesday, after President Vladimir Putin last year urged that the development of the field be speeded up.

Tomtor, located in the north of the Siberian region of Yakutia, is a key project in Russia's plans to boost output of the metals that are used in the defence industry and in making mobile phones and electric cars, to reduce reliance on imports from China.

According to an official state registry of Russian companies, Rosneft secured complete control over the project's operator, Vostok Engineering, on May 20.

Rosneft did not immediately reply to a request to comment.

In November Putin accused the operator of Tomtor of delaying the deposit's development, suggesting it should either raise investment or seek help from third parties, including the state.

Before the Ukraine conflict, Russia planned to invest $1.5 billion in rare earth minerals, striving to become the biggest producer after China by 2030.

Other countries, including the United States, are also trying to curb their reliance on China, which controls 95% of the global production and supply of rare earth metals.

Businessman Alexander Nesis, a former shareholder in Polymetal, a major producer of gold and silver, used to own a 75% stake in a firm called ThreeArc Mining, the operator of the project, through his IST group of companies.

Polymetal used to own a 9.1% stake in ThreeArc Mining.

Following the ownership change after the start of Russian military action in Ukraine, and subsequent Western sanctions on Russian businesses, the operator of the project ended up under control by IST's former manager Vladislav Resin, before Rosneft gained it.