Ukrainian security officials say mass killings of protesters in February were conducted under the "direct leadership" of President Viktor Yanukovich. (Reuters)

Government officials on Thursday blamed Ukrainian special police units directed by then-President Viktor Yanukovych and supported by Russian agents for killing some of the 76 people who died in the center of Kiev in February.

The mystery of the deaths — many of them the result of sniper fire — has provoked numerous sinister theories. Ukrainians consider finding the killers a crucial test of their new government, not only of its competence but its commitment to transparency.

Russian President Vladimir Putin accused the demonstrators themselves of the shootings, which he described as an effort to discredit the Yanukovych government. Russian officials have also accused the United States of having a hand in the deaths by providing money they said was used to pay hired killers, assertions U.S. officials have called absurd. In an interview with the Associated Press on Wednesday, Yanukovych said he had nothing to do with the deaths.

The killings occurred Feb. 18-20 after three months of what had been mostly peaceful demonstrations by protesters demanding Yanukovych’s ouster, an end to corruption and better government. The death toll is about 100 as some of the wounded have since died.

During a news conference Thursday, Interior Minister Arsen Avakov said preliminary results of the inquiry had found that Berkut riot police had killed 17 of the protesters. Twelve Berkut officers connected to the deaths had been identified, he said, and police have begun arresting them. Special Alpha unit troops were also accused of involvement. Officials said some suspects had fled to Crimea, which officials there denied.

The new head of Ukraine’s Security Service, Valentyn Nalyvaychenko, said he suspected that his counterpart agency, the Russian FSB, had been in Ukraine to help plan suppression of the demonstrations.

“We do not comment on groundless accusations,” an FSB spokesman told Interfax in Moscow on Thursday. “Let these statements be on Nalyvaychenko's conscience.”

Nalyvaychenko said warrants had been issued for the arrests of Oleksandr Yakymenko, his predecessor as head of the security services, and for Yanukovych.

Many of the deaths occurred amid the smoke and flames of burning tires that enveloped Instytutska street, just off Independence Square, known as the Maidan. Some protesters had set up barricades of burning tires and mounds of sandbags, throwing Molotov cocktails at police to prevent them from entering the Maidan.

Two days after the shootings, on Feb. 22, Yanukovych fled the country for sanctuary in Russia. A few days after that, Russia began moving special troops into Ukraine’s Crimean peninsula and annexed the territory after a speedily arranged referendum March 16 in support of the move.

Early in March, a day after Putin accused the demonstrators of killing their own, Russian-owned television reported on the leaked tape of a telephone conversation between Urmas Paet, the Estonian foreign affairs minister, and Catherine Ashton, head of foreign affairs for the European Union.

The conversation, widely believed to have been recorded by Russian security, suggested that a doctor at the scene of the shootings believed snipers were shooting at both sides. The doctor, Olga Bogomolets, said last week she had never made such an assertion.

To suggest otherwise, she said, was either a lie or a misunderstanding. “I am not a criminal expert,” said Bogomolets, who became a hero of the revolution because of her efforts to save lives — she had turned the lobby of the nearby Ukraina Hotel into an emergency room. “I was just trying to keep people from dying.”

Now Ukrainians want a thorough investigation, she said.

“We have to find the truth,” she said. “We are tired of living with corruption and lies.”