A pair of police officials patrol on a bridge outside the Kremlin in Moscow on March 26, 2018. (AFP PHOTO)

MOSCOW, March 26 (Xinhua) -- The Russian Foreign Ministry said Monday that Russia "strongly protests" diplomats expulsion by the United States and 14 European countries over an ex-spy case, vowing to retaliate.

"We consider this step as unfriendly and not corresponding to the goal and wish to establish the causes and search for the perpetrators of the (ex-spy poisoning) incident on March 4," the ministry said in a statement.

It said the British authorities took a "prejudiced, biased and hypocritical stance." It denied Russia's involvement in the incident.

U.S. President Donald Trump has ordered the expulsion of 60 Russian diplomats and intelligence officials, and the closure of the Russian Consulate in Seattle in response to the ex-spy poisoning case, senior U.S. officials said Monday.

On the same day, European Council President Donald Tusk announced that a total of 14 member states of the European Union have also decided to expel Russian diplomats.

They accused Moscow of launching a chemical attack against a Russian ex-spy in Britain earlier this month.

Sergei Skripal, 66, a former Russian intelligence officer, and his 33-year-old daughter Yulia were found unconscious on a bench at a shopping center in Salisbury on March 4.

They remain in critical condition after exposure to a nerve agent, which, according to the British authorities, could have originated from Russia.

Moscow has denied any involvement in the incident and insisted on participating in direct investigation into the case.

"Britain's allies also have no objective and exhaustive data, but they blindly follow the principle of Euro-Atlantic unity at the expense of common sense, standards of civilized interstate dialogue and international law principles," the Russian Foreign Ministry said Monday.

Kremlin spokesman Dmitry Peskov said that Moscow regrets the moves of the Western countries and will analyze the situation and propose response measures to President Vladimir Putin to make a final decision.

On March 14, British Prime Minister Theresa May announced a series of measures against Russia following the poisoning incident, including the expulsion of 23 Russian diplomats.

In retaliation, Moscow expelled an equal number of British diplomats and closed a British consular mission.