LONDON (Reuters) - Britain will expel 23 Russian diplomats in retaliation for the nerve agent attack on a former Russian double agent, Prime Minister Theresa May said on Wednesday.

“Under the Vienna Convention, the United Kingdom will now expel 23 Russian diplomats who have been identified as undeclared intelligence officers,” May told parliament. “They have just one week to leave.”

May said the biggest expulsions from London in 30 years would degrade Russian intelligence capabilities in Britain for years to come.

“We will freeze Russian state assets wherever we have the evidence that they may be used to threaten the life or property of UK nationals or residents,” May said.