BELGRADE: Serbian President Aleksandar Vucic on Friday opened a portion of a Russian gas project running through his country and hailed it as key for the security of its energy supply.

The 403-kilometre(250-mile) long stretch -- from Zajecar in eastern Serbia to Horgos on Hungary border -- is part of the larger TurkStream pipeline which supplies Russian natural gas to Turkey and central Europe.

"This morning at 6:00 am (0500 GMT) gas from Bulgaria started to flow and entered the newly-built Serbia's pipeline.

"A big day for Serbia!" Vucic wrote on Instagram.

At a ceremony held in Gospodjinci in northern Serbia, Vucic hailed the opening of the so-called Balkan Stream pipeline as "key for Serbia's future development" that would enable the country's "energy stability and security".

Russian ambassador to the Balkan nation Aleksandar Bocan-Harcenko said the pipeline would "provide energy security also for the wider region, central Europe," the state-run RTS television quoted him as saying.

TurkStream is a landmark project of Turkey and Russia to deliver Russian gas via the Black Sea.

In July last year US Secretary of State Mike Pompeo described both TurkStream and Nord Stream 2 pipeline, which is to bring Russian gas to Germany, as "Kremlin tools to expand European dependence on Russian energy supplies" that "undermine Ukraine".

US President Donald Trump's administration has repeatedly slammed Germany and other European nations for their reliance on energy from Russia.

In 2019 it imposed sanctions on companies involved for the two projects.

Serbia, which aspires to join the European Union, has traditionally been an ally of Russia and is heavily dependant upon Russian gas.