Which nation is developing the Oreshnik hypersonic missile that was featured in the news?

Russia recently tested the Oreshnik hypersonic missile, which can hit targets in the western United States and Europe and has a range of 3,000–5,500 kilometres. Like intercontinental ballistic missiles (ICBMs), it is unique in that it may carry many warheads. The deployment of this missile, according to President Vladimir Putin, was a major escalation in the continuing conflict and was a reaction to Ukraine's use of Western weapons. There are currently no reliable defences against the missile, which is made to be extremely accurate.