MOSCOW -- Russia announced the expulsion of more than 150 diplomats, including 60 Americans, on Thursday and said it was closing a U.S. consulate in retaliation for the wave of Western expulsions of Russian diplomats over the poisoning of an ex-spy and his daughter in Britain, a tit-for-tat response that intensified the Kremlin's rupture with the United States and Europe. The Russian move came as a hospital treating Sergei Skripal and his daughter, Yulia, said the woman was improving rapidly and was now in stable condition, though her father remained in critical condition.

The Skripals were found unconscious and critically ill in the English city of Salisbury on March 4. British authorities blamed Russia for poisoning them with a military-grade nerve agent, accusations Russia has vehemently denied.

Two dozen countries, including the U.S., many EU nations and NATO, have ordered more than 150 Russian diplomats out this week in a show of solidarity with Britain -- a massive action unseen even at the height of the Cold War.

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Russian Foreign Minister Sergey Lavrov said at news conference Thursday that Moscow will expel the same number of diplomats from each of those countries in retaliation.

U.S. Ambassador Jon Huntsman was summoned to the Foreign Ministry while Lavrov was speaking, where he was handed notice that Russia is responding quid pro quo to the U.S. decision to order 60 Russian diplomats out.

In a statement, Huntsman said there was "no justification" for the move and that it shows Moscow isn't interested in dialogue with the United States about important matters.

"Russia should not be acting like a victim," U.S. State Department spokeswoman Heather Nauert said.

Lavrov also said Moscow will retaliate for the U.S. decision to shut the Russian consulate in Seattle by closing the U.S. consulate in St. Petersburg.

The Foreign Ministry said the U.S. diplomats, including 58 from the embassy in Moscow and two from the consulate in Yekaterinburg, must leave Russia by April 5. It added that the U.S. must leave the consulate in St. Petersburg no later than Saturday.

The ministry warned that if the U.S. takes further "hostile actions" against Russian missions, Russia will respond in kind.

"We invite the U.S. authorities who are encouraging a slanderous campaign against our country to come back to their senses and stop thoughtless actions to destroy bilateral relations," it said.

Lavrov emphasized that the expulsions followed "brutal pressure" from the U.S. and Britain, which forced their allies to "follow the anti-Russian course."

He also noted that the job of the international chemical weapons watchdog is to determine what chemical agent was used to poison Skripal and his daughter, not verify the British conclusions.

Lavrov said that Moscow called a meeting Monday of the secretariat of the Organization for the Prohibition of Chemical Weapons to discuss the case.

Meanwhile, Salisbury NHS Trust, which oversees the hospital where the Skripals are being treated, said Thursday that 33-year-old Yulia is "improving rapidly and is no longer in a critical condition. Her condition is now stable."

"She has responded well to treatment but continues to receive expert clinical care 24 hours a day," said Dr. Christine Blanshard, medical director at Salisbury District Hospital.

Sergei Skripal, 66, remains in critical condition, the hospital said.

Lavrov said that Russia would seek consular access to Yulia Skripal now that she has regained consciousness.

Sergei Skripal, a former Russian military intelligence officer, was imprisoned after he sold secrets to British intelligence. He was released in a 2010 spy swap and moved to Britain.

Britain says he and his daughter, who was visiting from Russia, were poisoned with a nerve agent developed in Soviet times and that it must have come from Russia.

Police say they were likely exposed to the poison on the door of Sergei Skripal's suburban home in Salisbury, where the highest concentration of the chemical has been found.

About 250 British counterterrorism officers are working on the investigation, retracing the Skripals' movements to uncover how the poison was delivered. They have searched a pub, a restaurant and a cemetery, and on Thursday cordoned off a children's playground near the Skripal home.

Russian Foreign Ministry spokeswoman Maria Zakharova said Thursday that Britain's allegation of Russian involvement in the poisoning was a "swindle" and an "international provocation." She said Russia continued to demand access to investigation materials, which Britain has refused to share.

Zakharova charged that Britain, the U.S., the Czech Republic and Sweden have all researched the nerve agent that London said was used to poison the Skripals.

She said that the Western research into the class of nerve agent, known as Novichok, was reflected in numerous open source documents of NATO members. Britain and its allies have dismissed previous Russian claims that they possessed that type of nerve agent.