The UK has been threated with a “military response” by Russia after pledging to send long-range missiles to Ukraine.

The UK’s defence secretary said Storm Shadow missiles will be provided to Ukraine‘s military – and Sky News understands that some of the missiles are already with Ukrainian troops.

In response to reports the deal had been done, Moscow said the move would require an “adequate response from our military”.

Ukraine has long been calling for long-range missiles, but the US and other countries have been unwilling to supply them in case strikes inside Russia lead to escalation.

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Storm Shadow is a long-range, air-launched cruise missile developed by British Aerospace and a French company, which carries a 450kg conventional warhead to a range of up to 200 miles (300km).

Speaking in the House of Commons, Mr Wallace said: “The donation of these weapons systems gives Ukraine the best chance to defend themselves against Russia’s continued brutality, especially the deliberate targeting of Ukrainian civilian infrastructure, which is against international law.

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“Ukraine has a right to be able to defend itself against this.”

He added that the missiles would be for use “within Ukrainian sovereign territory”.

Missiles being launched into Russia would raise the likelihood of a greater Russian reaction.

Mr Wallace said he would not give in-depth details of the capabilities of Storm Shadow – but said: “These weapons will give Ukraine new capability, members should recognise that these systems are not even in the same league as the Russian AS-24 killjoy hypersonic missile,” or “even the Kalibr cruise missile with a range of over 2,000 kilometres, roughly seven times that of a Storm Shadow missile”.

What are storm shadow cruise missiles?

The deployment of the Storm Shadow cruise missiles mark a significant step-up in the capabilities of arms the UK has sent to Ukraine.

The missile has a strike capability of nearly 200 miles (300km) – meaning it would potentially allow Ukraine to hit further into Russian territory.

The missile weighs 1.3 tonnes and is just over 5m long.

It is launched from the air, and in theory can be used from Ukraine’s Soviet-made jets.

UK-owned Storm Shadow missiles are made in Stevenage by MBDA. Each cruise missile costs an estimated £2m.

The Storm Shadow was originally developed as a project between the UK and France in the early 1990s.

It was used in Iraq in 2003, while France, Italy and the UK used it in Libya in 2011.

The missiles have also been used to bomb Islamic State targets in Syria and Iraq.

Ukrainian President Volodymyr Zelenskyy has pleaded with Western nations for these types of missiles for months – but the requests have been denied, especially by the US.

In his speech, the defence secretary laid out some of the ways Russia had been attacking Ukraine – including allegations it had used white phosphorous.

He said that using such weapons – “which burn at 800C” – is in contravention of “protocol three of the Convention of Certain Conventional Weapons”.