Russia is in the process of equipping its new nuclear submarines with hypersonic Zircon missiles, the head of Russia's largest shipbuilder told the RIA state news agency in an interview published on Monday.

"Multi-purpose nuclear submarines of the Yasen-M project will ... be equipped with the Zircon missile system on a regular basis," , Alexei Rakhmanov, chief executive officer of the United Shipbuilding Corporation (USC), told RIA.

"Work in this direction is already underway."

Yasen-class submarines, also known as Project 885M, are nuclear-powered cruise missile submarines, built to replace Soviet-era nuclear attack submarines as part of a programme to modernise the army and fleet.

The sea-based Zircon hypersonic missiles have a range of 900 km (560 miles), and can travel at several times the speed of sound, making it difficult to defend against them.

President Vladimir Putin said earlier this year that Russia would start mass supplies of Zircon missiles as part of the country's efforts to boost its nuclear forces.

The Russian multi-purposes frigate Admiral Gorshkov, which has tested its strike capabilities in the western Atlantic Ocean earlier this year, has been already equipped with Zircon missiles.

(Reporting by Lidia Kelly in Melbourne; Editing by Simon Cameron-Moore)