KIEV, Jan. 17 - The Ukrainian government on Thursday fired Ihor Voronin, the architect of a controversial natural gas agreement between Ukraine and Russia, as deputy chairman of Naftogaz Ukrayiny, the national oil and gas company.

Voronin, who also holds the post of the CEO of UkrGaz-Energo, Ukraine’s largest supplier of natural gas, has reportedly earlier this year taken long vacation, according to a source at the company.