MOSCOW -- Tensions between Russia and the West have reached heights not seen since the Cold War. Russia on Thursday ordered more than 150 diplomats -- including Americans -- out of the country. The move was in retaliation for the expulsion of Russian diplomats from two dozen Western countries over Russia's alleged involvement in the poisoning of an ex-spy in the U.K.

Jon Huntsman, the U.S. ambassador in Moscow, was summoned to the foreign ministry Thursday to be read the riot act by Russian officials. Foreign Minister Sergei Lavrov didn't mince his words: 60 U.S. diplomats have seven days to leave Russia. That's an exact match of the number of Russian diplomats that were expelled by the U.S. on Monday. The U.S. consulate in St. Petersburg will also be closed, and Lavrov warned it won't end there.

The tit-for-tat expulsions come after a Russian double agent and his daughter were poisoned by a military grade nerve agent in England. The deadly chemical set off panic and was internationally condemned. The agent, Novichok, was developed by Russia in the 1980s.

In all, 28 countries in the West have expelled 150 Russian diplomats since the attack.

In an interview before Thursday's expulsions, Huntsman said the nerve agent attack can't go unpunished.

"The message that is being sent is you cannot use a military-grade nerve agent on the streets of Salisbury against a British citizen and his daughter without a response," Huntsman said. But Russian Foreign Ministry spokeswoman Maria Zakharova said there was no proof Russia was to blame for the attack, and compared it to misleading information she said the West used to justify the invasion of Iraq.

"Nobody asked for some additional material on weapons of mass destruction, which Saddam Hussein was accused of having and using," Zakharova said. "Nobody asked for more evidence. They just trusted the U.S. and Great Britain, and they were betrayed."

On Thursday, the State Department said Russia had no justification for kicking out U.S. diplomats, and that it will only lead to further isolation for Russia.