The US is to impose new sanctions against Russia in the wake of the novichok nerve agent attack in the UK.

Former Russian double agent Sergei Skripal and his daughter Yulia were poisoned in Salisbury in March.

Both were taken to hospital in a critical condition.

Yulia was ultimately discharged in April, while Sergei was kept in hospital until mid-May.

Officials said that the nerve agent novichok - which was developed in the Soviet Union - was used in the attack.

The British government and a number of its allies blamed Russia for the attack - claims the Kremlin vehemently denied.

It provoked a spate of diplomatic expulsions from countries including Ireland, with Russia responding with tit-for-tat expulsions. 

The US State Department has now announced fresh sanctions against Moscow in response to the attack against the Skripals, again accusing Russia of responsibility.

In a statement, spokesperson Heather Nauert said: "Following the use of a 'Novichok' nerve agent in an attempt to assassinate UK citizen Sergei Skripal and his daughter Yulia Skripal, the United States, on August 6, 2018, determined [...] that the Government of the Russian Federation has used chemical or biological weapons in violation of international law or has used lethal chemical or biological weapons against its own nationals."

The department cited 1991 US legislation on chemical and biological weapons.

The new sanctions are set to come into effect on August 22nd, after a 15-day congressional notification period.

The sanctions come more than a month after the death of a British woman - Dawn Sturgess - following exposure to novichok.

Charlie Rowley - Dawn's partner, and who also fell ill after exposure to the substance - has said the nerve agent came in a bottle disguised as perfume.

Police have been investigating whether it was linked to the attack on the Skripals.