MOSCOW, July 5 (Xinhua) -- The Kremlin said Thursday it is concerned about a new poisoning incident in Britain following ex-spy Sergei Skripal's case that caused a diplomatic war between Russia and the West.

On Wednesday, London's Metropolitan Police confirmed that a British couple who were critically ill in the hospital have been poisoned by the same nerve agent used in an alleged attack on former Russian agent Skripal and his daughter.

"This is very disturbing news. Undoubtedly, it causes deep concern since a similar incident has already taken place in Britain," Kremlin spokesman Dmitry Peskov said.

Novichok, a toxic agent allegedly produced in Russia, was said to be used in March to poison Skripal and his daughter Yulia, both of whom survived and are now recovering at secret addresses.

Russia has repeatedly denied any involvement in the Skripal incident and offered to participate in the investigation.

The proposal of a joint investigation remains in force, but the British side isn't interested in it, Peskov said.

Britain's Security Minister Ben Wallace said in an interview with the BBC that he was "waiting for the phone call from the Russian state" to elaborate on the incidents.

Peskov said Moscow has no information about what substances were used in both cases.

Nikolai Kovalyov, former director of Russia's Federal Security Service, suggested an "authoritative international body" be set up under the aegis of the Organization for Security and Cooperation in Europe Parliamentary Assembly to investigate the incidents.