KIEV, Feb. 27 – Ukraine on Monday held the first stage of a tender to appraise the country's natural gas transportation system that moves bulk of Russian gas to markets in Europe, Naftogaz announced Monday.

Four companies – Thomas & Simonova, Duff & Phelps, Baker Tilly Ukraine, and Ernst&Young -- have submitted their applications, Naftogaz said in a statement.

Under conditions of the tender, during the first stage the participants submit their preliminary offers without stating the price of their services, it said.