Russia has deployed a new division of S-400 surface-to-air missiles in Crimea in an escalation of military tensions on the Crimean peninsula.
Russian annexed Crimea from Ukraine in 2014, triggering economic sanctions by the European Union and United States and a tense stand-off in the region.
The US said in December it planned to provide Ukraine with "enhanced defensive capabilities", which officials said included Javelin anti-tank missiles.
Moscow's latest deployment represents the second division armed with S-400 air defence systems on the peninsula, after the first in the spring of 2017 near the port town of Fedosia.
The new division will be based next to the town of Sevastopol and will control the airspace over the border with Ukraine, the RIA news agency reported on Saturday.
The new air defence system, designed to defend Russia's borders, can be turned into combat mode in less than five minutes, Interfax news agency quoted Viktor Sevostyanov, a commander with Russia's air forces, as saying.
Russia's defence ministry says the S-400 systems, known as Triumph, can bring down airborne targets at a range of 400 kilometres and ballistic missiles at a range of 60 kilometres.
They were first introduced to the Russian military's arsenal in 2007, the ministry said.