Russia says US sanctions over nerve agent attack 'unacceptable'

The Kremlin on Thursday slammed as "unacceptable" US sanctions over Moscow's alleged involvement in a nerve agent attack in Britain, but said Russia still hopes for constructive relations with Washington.

"We consider categorically unacceptable the linking of new restrictions, which we as before consider illegal, to the case in Salisbury," Kremlin spokesman Dmitry Peskov told journalists, referring to the nerve agent attack on former double agent Sergei Skripal.

He added that "Moscow retains hopes of building constructive relations with Washington."

Russian markets tumbled after Washington announced the sanctions late on Wednesday, with the ruble falling to its lowest value in almost two years.

The US State Department called them a response to "the use of a 'Novichok' nerve agent in an attempt to assassinate UK citizen Sergei Skripal" -- who was a double agent -- and his daughter Yulia in March.

The action is aimed at punishing President Vladimir Putin's government for having "used chemical or biological weapons in violation of international law," State Department spokeswoman Heather Nauert said in a statement.

The Skripals survived the attack but a British couple was poisoned by the same Novichok agent in a nearby town, one of whom, 44-year-old Dawn Sturgess, subsequently died.

Moscow has angrily rejected any involvement, plunging diplomatic relations with London into a crisis.

The UK on Thursday welcomed the measures, that come less than a month after US President Donald Trump met Putin at a historic summit in Helsinki.

The Russian economy is still reeling from the 2014 international sanctions imposed on Moscow over its actions in Ukraine and a crash in oil prices the same year.

While Russia returned to growth in 2017 after two years of recession, it pales in comparison with growth figures seen during Putin's first two terms in office from 2000 to 2008 thanks to soaring oil prices.