LONDON (AP) — The Latest on the poisoning of a former Russian spy in Britain (all times local):
The chairwoman of the upper chamber of the Russian parliament says Britain is trying to influence this weekend's Russian presidential election by accusing Moscow of poisoning an ex-spy.
Sergei Skripal and his daughter were poisoned with a military-grade nerve agent in an English city last week and are in the hospital in critical condition.
Valentina Matviyenko, who is the third most senior official in Russia, said on Tuesday the British prime minister's statement aims to "exert influence and pressure" on the March 18 vote.
British Prime Minister Theresa May said on Monday Russia is "highly likely" to be responsible for the attack.
A former chief of Russia's main domestic intelligence agency says another post-Soviet nation could be the source of a rare nerve agent that Britain said was responsible for poisoning a Russian ex-spy in an English city last week.
British Prime Minister Theresa May said on Monday that Russian ex-spy Sergei Skripal and his daughter had been poisoned with Novichok, a military-grade nerve agent of a type developed in the Soviet Union near the end of the Cold War.
Nikolai Kovalyov, former chief of the FSB, told the Russian news agency on Tuesday that Novichok used to be stored in different parts of the Soviet Union, including Ukraine, which have since become independent nations, and that Ukraine or another post-Soviet nation could be the source of it.
Britain has asked the Russian ambassador in London to explain how the nerve agent turned up in the English city of Salisbury, leaving Skripal and his adult daughter in critical condition.
Russian news agencies say the Foreign Ministry has summoned the British ambassador in Moscow over the poisoning of a Russian ex-spy.
The foreign ministry was quoted by Russian wires as saying that the ambassador must visit the ministry later on Tuesday.
Britain says a military-grade nerve agent developed by the Soviet Union was used in the poisoning of Sergei Skripal and his daughter Yulia. It has demanded a response from Moscow.
The chief of the world's chemical weapons watchdog says that those responsible for the nerve agent attack on a former Russian spy and his daughter "must be held accountable."
In a speech Tuesday to the Executive Council of the Organization for the Prohibition of Chemical Weapons, Director-General Ahmet Uzumcu said British Foreign Secretary Boris Johnson called him Monday evening to inform him of the results of investigations into the attack on 66-year-old Sergei Skripal and his 33-year-old daughter Yulia.
British Prime Minister Theresa May told Parliament that Russia is "highly likely" to blame for poisoning Skripal and his daughter with a military-grade nerve agent.
Uzumcu says that, "It is extremely worrying that chemical agents are still being used to harm people. Those found responsible for this use must be held accountable for their actions."
Uzumcu's comments to the closed-door meeting were released by the OPCW.
Foreign Minister Sergey Lavrov says Russia will only cooperate with Britain on the investigation into last week's poisoning of an ex-Russian spy if it receives samples of the nerve agent that is believed to have sickened the ex-spy and his daughter.
Lavrov told reporters on Tuesday Moscow's requests to see samples of the nerve agent have been turned down, which he called a violation of the Chemical Weapons Convention, which outlaws the production of chemical weapons. He insisted that Russia is "not to blame" for the poisoning.
British Prime Minister Theresa May said on Monday Russian ex-spy Sergei Skripal and his daughter had been poisoned with a military-grade nerve agent of a type developed in the Soviet Union. May said Russia has until the end of Tuesday to explain how the substance ended up in Britain.
Lavrov said on Tuesday Moscow is willing to cooperate with the probe but suggested that London would be "better off" complying with its international obligations "before putting forward ultimatums."
Britain's government is considering how to deal with the poisoning of an ex-spy as it awaits a Russian government response to its claim that Russian was involved.
Officials said Tuesday Prime Minister Theresa May is reviewing a range of economic and diplomatic measures.
May has said it is "highly likely" Russia was involved in the nerve agent poisoning of 66-year-old Sergei Skripal and his 33-year-old daughter Yulia. Both remain in critical condition.
The prime minister says Russia has until the end of Tuesday to explain its actions in the case, which focuses on a former Russian military intelligence officer who was convicted of spying for Britain and then released in a spy swap.
Former foreign minister David Miliband has urged May to seek support from Europe and the United States.