US President Donald Trump is expelling 60 Russian diplomats from the US-based Russian Embassy and permanent mission to the UN.

The measures are in retaliation for the poisoning of the former spy Sergei Skripal in Britain on March 4.

Fourteen European Union member states and several other countries have also announced plans to expel diplomats.

Russia condemned the expulsions as an "unfriendly act" and vowed to take action.

The United States will expel 60 Russian diplomats in response to the poisoning of the Russian former spy Sergei Skripal in Britain.

The measure was announced Monday morning, two weeks after Britain first accused Russian President Vladimir Putin's government of being behind the nerve-agent attack.

The Trump administration will remove Russians from their posts at the US-based Russian Embassy and permanent mission to the United Nations, The Wall Street Journal reported. The Journal said the US also planned to close the Russian consulate in Seattle, which is close to a US naval facility.

Moscow has denied involvement in the March 4 poisoning of Skripal and his daughter, but evidence presented by Britain privately to allied nations resulted in widespread condemnation and, ultimately, the removal of diplomats.

Britain expelled 23 diplomats from the Russian Embassy in London shortly after blaming Russia for the attack.

Russia responded in kind, demanding the departure of an equal number of British diplomats working in Moscow.

A White House statement on Monday said:

"The United States takes this action in conjunction with our NATO allies and partners around the world in response to Russia's use of a military-grade chemical weapon on the soil of the United Kingdom, the latest in its ongoing pattern of destabilizing activities around the world.

"Today's actions make the United States safer by reducing Russia's ability to spy on Americans and to conduct covert operations that threaten America's national security."

UK Prime Minister Theresa May and Trump in September 2017. REUTERS/Kevin Lamarque

Around the same time as the White House made its announcement, other European countries announced their own expulsions in what appeared to be a coordinated show of solidarity.

European Council president Donald Tusk said that unspecified "additional measures, including further expulsions," could follow.

Prime Minister Theresa May told the British parliament on Monday afternoon that this was the "largest collective expulsion of Russian intelligence officers in history." It is significant that she referred to the dismissed officials as intelligence officers, rather than diplomats.

Russia's Foreign Ministry condemned the widespread expulsions as an "unfriendly act" and vowed to retaliate.

It said in a statement, cited by Reuters:

"The provocative gesture of solidarity with London by these countries, who have bowed to the British authorities in the so-called Skripal affair and did not bother to understand the circumstances of what happened, is a continuation of the confrontational path to escalation.

"Britain's allies... are blindly following the principle of Euro-Atlantic unity, to the detriment of common sense, the norms of civilized international dialogue, and the principles of international law.

"It goes without saying that this unfriendly act by this group of countries will not go without notice and we will react to it."

Here are all the countries and intergovernmental bodies that have expelled Russian officials over the attack:

The UK — 23 diplomats expelled

United States — 60

NATO — 7

Albania — 2

Australia — 2

Canada — 4

Croatia — 1

Czech Republic — 3

Denmark — 2

Estonia — 1

Finland — 1

France — 4

Germany — 4

Ireland — 1

Italy — 2

Latvia — 1

Lithuania — 3

Moldova — 3

Netherlands — 2

Norway — 1

Poland — 4

Romania — 1

Ukraine — 13

Spain — 2

Sweden — 1

The total figure is 148.