PRAGUE (Reuters) - Nerve agents of the Novichok type though not the same as that used to poison a former Russian spy in Britain have been synthesized in tiny amounts in the Czech Republic to help train the army against chemical warfare, the government said.

The Czech Republic had been listed among others by Russia as potential source of the Novichok-like substance that left ex-double agent Sergei Skripal and his daughter Yulia in critical condition in the English city of Salisbury on March 4.

The Czech Defense Ministry said that it had carried out “microsynthesis” of several micrograms at a time of potential chemical warfare agents, including Novichok and sarin gas. This did not amount to production as understood under international treaty and could not have leaked, it said.

“Substances referred to as ‘Novichok’ in the press, among them the A230 substance, are potential poisonous chemical substances, whose identification ... is part of the training of Czech anti-chemical military units,” a ministry statement said.

“The tested substance originates in a tube solely for the purpose of measuring spectral data and the content is always immediately destroyed after testing, in line with regulations and the Czech Republic’s commitments,” it said. “The probability of a leak, therefore, equals zero.”

The Foreign Ministry said separately that the A230 type tested in the Czech Republic was different from the substance known as A234 that had been used in the Skripal assault.

The Czech government said earlier the substance used in Skripal’s poisoning could not have come from the Czech Republic.

Britain accused Russia of being behind the March 4 attack on the Skripals. Moscow has denied any involvement.

The New York Times quoted Ahmet Uzumcu, director general of the Organization for the Prohibition of Chemical Weapons, as saying on Thursday that about 50 to 100 grams of liquid nerve agent were used in the Skripal poisoning. That would be significantly larger amount than what would be created in a laboratory for research purposes, Uzumcu said.

Information on the Czech testing was requested by President Milos Zeman, who has repeatedly taken pro-Russian positions on international issues such as the war in Ukraine and EU sanctions against Moscow.

The Czech government, which is in charge of foreign policy, expelled three Russian diplomats as part of the European response to the attacks on the Skripals.