BRUSSELS, March 19 (Xinhua) -- Foreign ministers of the European Union (EU) on Monday threw their weight behind Britain in a row with Russia over the poisoning of a former Russian spy.

In a strong-worded statement released following their monthly meeting, EU foreign ministers said the 28-member bloc "strongly condemns the attack" and "expresses its unqualified solidarity with the UK and its support, including for the UK's efforts to bring those responsible for this crime to justice."

The EU "takes extremely seriously the UK government's assessment that it is highly likely that the Russian Federation is responsible," said the statement.

The statement was released after British foreign secretary Boris Johnson debriefed his counterparts in the EU foreign affairs council, amid brewing tensions between London and Moscow.

The Russian Foreign Ministry expelled 23 British diplomats on Saturday in a retaliatory move over British punitive measures against Russia and the former Russian spy attack row.

The ministry also revoked its approval of the opening and operation of the British Consulate General in the Russian city of St. Petersburg.

Russia has notified London of the retaliatory measures in relation to the so-called "Skripal case", British Ambassador to Russia Laurie Bristow confirmed on Saturday after being summoned to the foreign ministry.

On Wednesday, British Prime Minister Theresa May announced a series of measures against Russia over its failure to respond to the British government's request to explain how a military-grade nerve agent was used in a recent attack on former Russian spy Sergei Skripal and his daughter.

The measures included the expulsion of 23 diplomats in a week, the freezing of Russian state assets in Britain, the suspension of all planned high-level bilateral contacts and boycotting the ministers and the royal family from attending the FIFA World Cup in Russia.

Skripal, a former Russian intelligence officer, and his 33-year-old daughter Yulia Skripal were found unconscious on a bench at a shopping center in Salisbury, Wiltshire earlier this month, and remain still in critical condition, according to reports.

The British government said they were poisoned with Novichok, a nerve agent.

The Russian government has denied any involvement in the incident.