Russia's trade surplus rose 70.8 percent year on year to 119.9 billion U.S. dollars in the first eight months of 2018, the Russian central bank said Tuesday, quoting preliminary estimates.

The surplus in the trade balance was caused by favorable price conditions for exports of energy products and moderately grown imports, the Bank of Russia said in a statement.

According to Russian Customs data, the country's trade surplus in January-July this year rose 55.4 percent from the same period a year ago. Its January-August data are not yet available.

The surplus in the current balance of payments of Russia, according to the central bank's preliminary estimate, amounted to 69 billion dollars in January-August 2018 against 19.1 billion dollars in the same period of 2017, the bank's statement said.

The surplus in the current account of the balance of payments has been the source of building up the country's international reserves and financing exports of capital, mostly, in the form of reducing external liabilities, it said.

Net private capital exports in January-August 2018, according to the Bank of Russia's estimate, reached 26.5 billion dollars against 9.6 billion dollars in January-August 2017.

Russia's international reserves gained 36.1 billion dollars, primarily due to the acquisition of foreign currency within the framework of the budgetary rule designed to shield the economy from swings in oil prices and protect the country's reserves, it said.

According to the budgetary rule, Russia uses additional revenues from energy exports to build up its reserves.