Russia said Thursday the British government should apologise after London demanded Moscow explain itself regarding a couple who fell ill in a new case of exposure to a nerve agent.
"I am sure that for everything that Theresa May's government has stirred up, this government and its representatives will have to apologise to Russia and the international community," foreign ministry spokeswoman Maria Zakharova told reporters.
"As is tradition in Britain, it will happen later but it will happen."
Meanwhile, the Kremlin said on Thursday (July 5) it had offered Britain its assistance in investigating a nerve agent attack on a Russian former spy and his daughter in Salisbury in March long ago, but had been rebuffed.
Britain called on Russia to give details about the Novichok nerve agent attack on a former double agent and his daughter after two British citizens were struck down with the same poison.
The two Britons, a 44-year-old woman and a 45-year-old man, were critically ill after an apparently chance encounter with the poison near the site of the March attack on ex-double agent Sergei Skripal and his daughter Yulia.
Britain accused Russia of poisoning the Skripals with Novichok - a nerve agent developed by the Soviet military during the Cold War - in what is the first known offensive use of such a chemical weapon on European soil since World War Two.
Russia, which is currently hosting the soccer World Cup, has denied any involvement in the March incident and suggested the British security services had carried out the attack to stoke anti-Moscow hysteria.