According to Reuters, 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.
Earlier this year, President Vladimir Putin had said that Russia would start mass supplies of Zircon missiles as part of the country's efforts to boost its nuclear forces.
"We will continue mass production of air-based hypersonic Kinzhal systems and will start mass supplies of sea-based Zircon hypersonic missiles," he had said.
Putin had made his remarks on February 23, two days after announcing Russia would suspend the New START treaty, its last remaining arms control agreement with Washington. The treaty limits each country's deployed nuclear warheads.
The news agency reported that the Russian multi-purpose frigate Admiral Gorshkov, which tested its strike capabilities in the western Atlantic Ocean earlier this year, has been already equipped with Zircon missiles.
