European Commission President Ursula von der Leyen on Saturday hailed a "new era" as a long-awaited pipeline began pumping gas, amid the EU's efforts to wean itself off Russian energy.
The Gas Interconnector Greece-Bulgaria (IGB), a 182-kilometre (113-mile) trans-boundary pipeline was designed to help Bulgaria, which has for years been heavily dependent on Russian gas, obtain energy from other sources.
It officially opened in July, but did not start operations until Saturday.