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Media captionSajid Javid says the suspects will “probably never” leave Russia

The two suspects in the Salisbury nerve agent attack will be caught and prosecuted if they ever step out of Russia, the minister of the interior has warned.

Sajid Javid, however, did recognise “the reality is we will probably never assure them in the UK”.

He told the BBC the pair, thought to be from Russia's military intelligence service, the GRU, were acting on orders from the “highest level” in Moscow.

Ex-Russian spy Sergei Skripal and his daughter Yulia were poisoned in March.

The suspects are understood to have travelled to the UK from Moscow on 2 March on Russian passports, under the aliases Alexander Petrov and Ruslan Boshirov.

Two days later, police say they sprayed the nerve agent, Novichok, on the front doorway of Mr Skripal's home in the Wiltshire city of Salisbury, before travelling home to Russia afterwards that day.

The attack left Mr Skripal, 66, and his 33 -year-old daughter hospitalised for weeks.

Speaking on BBC One's Andrew Marr show, Mr Javid called it a “sickening and despicable” attack.

It was “unequivocally, crystal clear this was the act of the Russian nation – two Russian nationals sent to Britain with the sole purpose of carrying out a reckless assassination attempt, ” he said.

“If they ever step out of the Russian Federation, Britain and its allies will get them and we will bring them to prosecution, ” Mr Javid added.

Last week, the UK secured the support of the US, France, Germany and Canada at a UN Security Council meeting, at which they agreed with the UK's assessment that Russia's government “almost certainly” approved the poisoning.

Russia dismissed the UK's evidence as “lies” and accused it of “disgusting anti-Russian hysteria”.

What happened to the Skripals ? Russia's scorn for ‘cheap soap opera' World leaders back UK Novichok accusations Image caption The home secretary says the suspects will “probably” never return to the UK