Here are the main developments since the poisoning of a Russian former double agent in England sparked soaring diplomatic tensions between London and Moscow.
Poisoning in English city
On March 4 spy Sergei Skripal, 66, and his daughter Yulia, 33, are found unconscious, slumped on a bench outside a shopping centre in Salisbury. They are currently in critical condition in a local hospital.
Skripal is a former colonel in Russian military intelligence who was jailed in his country for betraying agents to Britain's MI6 secret service and moved there in a spy swap in 2010.
On March 7 police say that the father and daughter have been poisoned by a highly toxic nerve agent.
London Accuses Moscow
On March 12 British Prime Minister Theresa May says it is "highly likely that Russia was responsible for the act", saying Moscow could be directly to blame or may have "lost control" of the nerve agent.
She tells British lawmakers that the military-grade nerve agent used was identified as belonging to a group of nerve agents known as Novichok and of a type developed by Russia.
Called "newcomer" in English, Novichok refers to a group of powerful and deadly chemical compounds reportedly developed by the Soviet government towards the end of the Cold War in the 1970s and 1980s.
Moscow rejects the claims as "provocation".
The US says it stands "in solidarity" with Britain. France and Germany make similar statements the following day.
On March 13 Russian Foreign Minister Sergei Lavrov says that Moscow is "not guilty" of the poisoning and is ready to cooperate with London.
Two days later Lavrov's deputy Sergei Ryabkov says Moscow never had any programmes to develop the Novichok nerve agent.
On March 14 London says that Moscow is "culpable" and it will expel 23 of the 59 Russian diplomats present in the United Kingdom.
It also suspends high-level diplomatic contact with Moscow and will keep royals at home during the 2018 football World Cup.
Russia's foreign ministry slams London's "choice for confrontation", adding that retaliation will follow shortly.
On March 15 Britain, France, Germany and the US say in a rare joint declaration that "there is no plausible alternative explanation" to Russian involvement and call on Moscow to provide "full and complete disclosure" of the Soviet-era chemical programme that developed Novichok.
The 29-member NATO alliance expresses solidarity with Britain over what it calls the first offensive use of a nerve agent on the military alliance's territory since World War II.
On March 16 British Foreign Secretary Boris Johnson says it is "overwhelmingly likely" that Russian President Vladimir Putin was behind the poisoning. The Kremlin says the accusation is "unforgivable".
The European Union's 28 national leaders are to discuss the attack at a Brussels summit on March 22-23, with president Donald Tusk saying the bloc would send a "clear message." However German Chancellor Angela Merkel says that the EU will not in the first instance discuss a boycott of the World Cup.
Russia opens a probe into the "attempted premeditated murder" of Yulia Skripal.
It also says it has begun a separate probe into the suspected murder of a Russian living in London, Nikolai Glushkov. On the same day the British police launch a murder probe into Glushkov's death.
On March 17, on the eve of the election which is widely expected to give Putin a fourth term, Russia says it will expel 23 British diplomats and halt the activities of the British Council in Russia following London's "provocative" measures.
Get the latest election news, live updates and election schedule for Lok Sabha Elections 2019 on ndtv.com/elections. Like us on Facebook or follow us on Twitter and Instagram for updates from each of the 543 parliamentary seats for the 2019 Indian general elections.