KYIV -- They all met their violent deaths, or came close to it, as war in Ukraine simmered. But their end came not in the country's eastern battlefields, but in busy urban streets far from the front lines.

They were the targets of car bombings and point-blank shootings, all carried out in broad daylight and most in the heart of the Ukrainian capital. The latest victim died on September 8 in a fiery explosion that reverberated through central Kyiv during evening rush hour.

The brazen assassinations and attempted assassinations have shaken and baffled the country since the first unexplained killing, that of a prominent journalist in July 2016. Nobody knows for sure who or what exactly is behind the assassinations, or whether any of them are directly connected.

Not a single case has been solved, and there have been no convictions. The perpetrator in one case was apprehended, and another was identified after being shot and killed. But neither have provided enough information to directly tie them to those the Ukrainian authorities consider the main suspects -- the Russian security services.

Officially, Ukraine is investigating all leads. But Artem Shevchenko, a spokesperson for Ukraine's Interior Ministry and National Police, told RFE/RL recently that officials believe all of the killings are "connected by the method used in each crime; I mean, by the explosions," a trait he claimed is indicative of the involvement of Russia's security services. He accounted for the shootings by suggesting the targets in those cases were Russians whom Moscow considered enemies of the state and wanted dead.

In fact, there is reason for many to suspect a "Russian trace," a term that has become ubiquitous among nearly all investigations into acts of sabotage and violence in Ukraine, including all of the assassination cases. The killings come as Ukraine's military fights an armed conflict with Moscow-backed separatists in its eastern regions. As part of the conflict, Kyiv says, Moscow has waged a "hybrid war" -- a military tactic that combines conventional and irregular warfare, propaganda, and cyberattacks -- against the former Soviet republic, which the Kremlin still sees as existing within its sphere of influence.

Despite mounting evidence, the Kremlin has denied supporting the separatists in the conflict, which has killed more than 10,000 people. Russia has also denied involvement in any of the killings, an argument that is seen as more credible.

Experts say -- and Ukrainian security officials have admitted to RFE/RL behind closed doors -- that there is not enough evidence in any case to say beyond a reasonable doubt that Russia ordered the killings or trained the killers.

Hired Assassins?

Mark Galeotti, a senior researcher at the Institute of International Relations in Prague and an expert on Russia's security services, agrees with Kyiv's official line to the extent that the perpetrators in each case are likely to have been trained by a state organization, given the methods and precision involved; in only one bombing was someone other than the target seriously injured.

But he tells RFE/RL that this does not necessarily mean Russia is that state.

"You can buy it or hire it in Kyiv and Moscow; it's not that expensive, unfortunately," Galeotti says of lethal talent. He says the former Soviet territory has suffered from a "hemorrhage of expertise out of the security realm, and likewise so many who moonlight out of it."

And there are some who believe Ukraine could be ignoring or covering up traces that lead to some of its own because they would undermine its message.

"In fact, it's significant that we don't have answers from Kyiv," Galeotti notes.

"In general terms, it could well be that Kyiv wants to keep it open because doing so serves its purpose and narrative," Galeotti continues. "But that would be a tactical error, because then it makes it seem that there's nothing the SBU [Security Service of Ukraine] can do" to prevent Russia from attacking Ukraine deep inside its own territory.

For now, there are more questions than answers in each of the seven assassinations and one assassination attempt, which RFE/RL highlights here:

The Killings

Timur Makhauri, killed, September 8, 2017

Makhauri, an ethnic Chechen with Georgian citizenship, was driving with his wife and her daughter in central Kyiv when his car suddenly exploded, killing him instantly and critically wounding his wife, who later reportedly lost her leg. The child was hospitalized but was not seriously injured.

As Ukraine's national police put it, Makhauri was no angel. He was allegedly involved in arms trafficking in Ukraine and was arrested earlier this year for illegal gun possession, police said.

According to the Hromadske news channel, which interviewed Makhauri before his death, he was credited by some as being the person behind the 2006 killing of Shamil Basayev, a Chechen separatist warlord infamous for his role in the 2004 Beslan school hostage crisis.

Makhauri also fought in the 2008 Russia-Georgian war and, in 2012, according to Hromadske, he moved to Syria, where he said he trained people to fight against President Bashar al-Assad. Shortly thereafter he was arrested on murder charges in Turkey and jailed for 3 1/2 years, until 2016, when he came to Ukraine.

Makhauri fought with other ethnic Chechens on the Ukrainian side in the conflict against Russia-backed separatists.

Makhauri's friends told RFE/RL at the scene of his death that they believed Russia was behind it. They dismissed his alleged ties to the criminal underworld and the possibility that someone from there might have come after him to settle a score.

Ukrainian authorities told RFE/RL that they have no leads in the case, but suspect Russia, or perhaps Chechen leader Ramzan Kadyrov -- whom they claimed was an enemy of Makhauri.

Yuriy Vozniy, killed, June 27, 2017

Vozniy's life ended when an undetermined blast struck the vehicle he was driving near the city of Kostyantynivka, about 50 kilometers west of the front line in the east of the country. The blast wounded three others in the vehicle.

Ukraine's military prosecutor's office, which is leading the investigation, has classified the incident as a terrorist act. There are no suspects, though some experts have pointed the finger at pro-Russian saboteurs. Few other details have been made public.

Maksim Shapoval, killed, June 27, 2017

Shapoval was killed hours before Vozniy but hundreds of kilometers away in Kyiv when an explosive device planted under his car detonated as he was driving shortly after 8 a.m.

Shapoval served in an elite Defense Ministry intelligence unit that conducted covert operations against Russia-backed insurgents in eastern Ukraine, according to local media and Ukraine's Defense Ministry.

Shevchenko told RFE/RL that Shapoval had recently returned from the conflict zone and the authorities believe the motive for what he called a "targeted assassination" was his "professional service."

Since the incident, authorities have qualified his killing as a "terrorist act," and they say Russia's Federal Security Service (FSB) is to blame. They have not shared evidence publicly to show this.

Adam Osmayev and Amina Okuyeva, survived, June 1, 2017

On June 1, a Chechen man posing as a French journalist shot Osmayev, leader of a pro-Ukrainian Chechen battalion, in Kyiv's Podil district. Osmayev's wife, Okuyeva, returned fire, wounding the would-be assassin, who was taken into custody. Osmayev made a full recovery.

WATCH: Amina Okuyeva Describes The Attack On Her Husband Adam Osmayev

Authorities later established that the shooter was a Russian national who had obtained a Ukrainian passport. They identified him as Artur Kurmakaev, born with the surname Denisultanov but also known by the nickname "Dingo," who is believed to have been involved in the 2009 killing of Umar Israilov, the former head security guard of Chechnya's Kadyrov. They have not, however, tied him directly to Russia's security services or Russian officials, including Kadyrov.

​Oleksandr Kharaberyush, killed, March 31, 2017

Kharaberyush, lieutenant colonel and deputy chief of the Donetsk region counterintelligence department for the SBU, died in a car bombing in the eastern port city of Mariupol on March 31.

The SBU has blamed Russia and the separatists it backs for the killing, saying it would "punish the terrorists who blew up the car ... as soon as possible."

Very little about the investigation has been made public since the incident, and the SBU did not respond to requests for comment.

​Denis​ Voronenkov​, killed, March 23, 2017

Voronenkov, a former Russian lawmaker and Putin supporter who turned Kremlin critic after fraud charges were brought against him and he fled to Ukraine, was gunned down on one of Kyiv's busiest street corners. Joining him in Ukraine was his wife, the former Russian lawmaker and opera singer Maria Maksakova. The newlyweds had only recently had a child.

The assassin came from behind and fired at Voronenkov's head at point-black range, wounding him before finishing him off after he fell to the ground. Voronenkov's bodyguard was also shot, but survived. He managed to fire back and fatally wound the assassin, a Ukrainian citizen who served in two volunteer militias.

Despite being Ukrainian, Kyiv claimed the shooter had been trained by and was working for Moscow, leading President Petro Poroshenko to call the assassination "an act of state terrorism by Russia." Authorities would eventually find a paper trail that showed the shooter traveling to and from Russia before the killing. Still, the evidence tying him to Russian authorities is not airtight.

A report on Russia's Rosbalt news site in September cited communication it obtained from Ukraine's Prosecutor-General’s Office that named Maksakova's ex, Russian Vladimir Tyurin, as well as a banker from Crimea, as the organizers of the killing. But Kyiv has not officially named them as suspects.

Ivan Mamchur, killed, September 16, 2016

Mamchur, a former commander and military intelligence official who worked at a prison in Rivne, western Ukraine, was shot and killed by Oleh Smorodinov, a resident of the southeastern Ukrainian city of Mariupol.

Ukrainian authorities blamed Russia, with Prosecutor-General Yuriy Lutsenko saying that it showed Russian intelligence services were "creating a network [to commit] terrorist attacks" on Ukrainian soil.

Smorodinov was detained while attempting to cross the border in Kharkiv Oblast. According to the Interfax-Ukraine news agency, Smorodinov confessed to killing Mamchur under an order from the FSB. Mamchur, he reportedly told his interrogators, was targeted for his service in the special forces and work in the conflict zone in eastern Ukraine.

​Pavel Sheremet, killed, July 20, 2016

Sheremet, a Belarusian-born Russian journalist who was often critical of top political leaders and government officials in Belarus, Russia, and Ukraine, was killed after a bomb detonated beneath his vehicle as he drove to a radio studio on a warm July morning.

A pretrial investigation into Sheremet's death "led to the conclusion that this crime was carefully prepared by a group of people," but it offered no names of suspects.

Security-camera footage from around the neighborhood where Sheremet lived and where the crime took place shows a man and a woman casing the area ahead of the bombing and even placing the bomb on Sheremet's vehicle. But they have not been identified, and authorities have refused to release footage showing the woman's face, they say for her protection.

An investigation by the Organized Crime and Corruption Reporting Project and Hromadske journalists found that an SBU agent was present at the scene when the bomb was placed on Sheremet's car and many witnesses were never interrogated.

An investigative report authored by this RFE/RL correspondent for the New York-based Committee to Protect Journalists (CPJ) found that "a greater amount of circumstantial evidence points to a Ukrainian trace [in the killing], raising questions about why authorities are pushing the Russian narrative and whether they may be covering up evidence to protect someone powerful."

