MOSCOW — Russia on Saturday ordered 23 British diplomats to leave the country within a week, escalating a diplomatic crisis after a former Russian spy and his daughter were poisoned with a military grade nerve agent on British soil.

The order came days after Prime Minister Theresa May of Britain expelled the same number of Russian diplomats and called off high-level contacts between the two governments.

The Russians also ordered the closing of the British Council, a cultural and educational organization, in Russia, and revoked permission for the British consulate general in St. Petersburg.

The announcement came after the British ambassador, Laurie Bristow, was summoned to the Foreign Ministry in Moscow on Saturday morning.