The US has activated a land-based missile defence station in Romania, which will form part of a larger and controversial European shield. The US says the Aegis system is a shield to protect Nato countries from short and medium-range missiles, particularly from the Middle East. But Russia sees it as a security threat – a claim denied by Nato.

Relations between the West and Russia have deteriorated since Moscow’s annexation of Ukraine’s southern Crimea peninsula in 2014. Nato Secretary General Jens Stoltenberg and other senior officials from the military alliance attended the opening ceremony at an old Romanian air base in Deveselu., 180km (110 miles) south-west of Bucharest.

The site hosts radar and SM-3 missile interceptors, and will be integrated into Nato’s missile shield when the bloc meets this summer. Both Nato and US officials have attempted to reassure Russia that the shield in Romania, and a similar one in Poland, does not undermine Russia’s strategic nuclear deterrent.

The defence system allows on-shore sites and warships to shoot down enemy ballistic missiles while they are still in space. The interceptor missiles are fired to hit missiles before they re-enter the atmosphere, stopping them well before there is any danger of causing any damage. The US is believed to have spent $800m (£554m) on the site in Romania, where work began in 2013.