Ukraine has integrated its electricity transmission network into the European energy system, Ukrainian President Volodymyr Zelensky said on Wednesday.

"Ukraine has become a member of the European Energy Union. The unification of Ukrainian and European energy systems has been completed," Zelensky tweeted.

Ukraine, which was importing electricity from Russia and Belarus, last year set a target to integrate its energy system into the European network of electricity transmission system operators by 2023.

According to media reports, 15 nuclear units at four Ukrainian nuclear power plants generate about 55 percent of Ukraine's electricity needs. Thermal power plants produce 29 percent of Ukraine's electricity, while the rest is powered by other sources or imported from abroad.