The UK is expelling nearly two dozen Russian diplomats, in response to the poison attack. This is marking a serious escalation of tension between Britain and Russia. CGTN's Catherine Drew reports from London.

British Prime Minister Theresa May returned to parliament after the passing of a deadline she'd set for Moscow to explain the use of what investigators say is a Russian made nerve agent -- in the poisoning of former double agent Sergei Skripal and his daughter Yulia earlier this month. May told the House of Commons that Russia has offered no credible explanation.

THERESA MAY BRITISH PRIME MINISTER "Under the Vienna Convention, the United Kingdom will now expel 23 Russian diplomats who have been identified as undeclared intelligence officers. They have just one week to leave. This will be the single biggest expulsion for over 30 years and it reflects the fact that this is not the first time that the Russian state has acted against our country."

Other measures announced by May include freezing some Russian state assets and increased checks on private flights, customs and freight shipments. May also said all high-level meetings between the UK and Russia would be suspended - and no Ministers or members of the Royal family would attend football's World Cup competition, hosted this year by Russia and set to begin in June. Russia has denied any involvement in the poisoning incident. The Russian Embassy in London called the expulsions unacceptable and short-sighted.

ALEXANDER VLADIMIROVICH YAKOVENKO RUSSIAN AMBASSADOR TO THE UK "We believe that the measures which are taken by the British government have nothing to do with the situation that we have in Salisbury, we believe this is very serious provocation and of course we are not ready to talk in the way of ultimatums."

Despite Moscow's insistence it had nothing to do with the events in Salisbury, observers here say the Prime Minister has broad support overseas.

WILL HEAVEN MANAGING EDITOR, THE SPECTATOR "I think there is a pretty significant amount of support for the UK. In her statement Theresa May said she had spoken to President Macron of France, Chancellor Merkel of Germany, President Trump."

British officials will continue to update the United Nations and NATO's North Atlantic Council on developments as the investigation continues and as three people remain hospitalized following the attack.

CATHERINE DREW LONDON "Having outlined steps Britain will take unilaterally, the British government is hoping in the days ahead to forge a coordinated international response to Russia in what is likely to be a test of allegiances. Catherine Drew, CGTN, London."