Police are treating the "targeted" poisoning of Sergei Skripal and daughter Yulia as attempted murder.
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MI6
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Police appeal for help from the public, as Sergei Skripal and his daughter Yulia remain critically ill.
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Joel Gunter
BBC News
A suspected poisoning in Salisbury led to renewed attention on a string of deaths in the UK.
Read moreSergei Skripal and his daughter remain critically ill as relatives say he feared for his safety.
Read moreA suspect in the poisoning of Alexander Litvinenko rejects suggestions that Russia was behind Sergei Skripal's collapse.
Sue Paz
BBC South
It's the centre of a modern-day mystery, but what do Salisbury residents make of its new-found fame?
Read moreVideo shows a man and a woman walking near to where an ex-Russian agent and his daughter were found collapsed in Salisbury, Wiltshire.
The pair are being treated, along with a member of the emergency services, after exposure to an unknown substance.
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The French, German and UK intelligence chiefs say their close partnership must continue.
Read moreIn his first ever UK broadcast interview, the former head of MI6 Sir Richard Dearlove said terrorism did not present a "systemic threat" to the nation.