At least 220 Russian soldiers were killed while fighting beside pro-Russian rebels in the East Ukraine war, according to the final report of slain politician Boris Nemtsov that was released on Tuesday. The report, which was finished by allies of the controversial opposition politician and may have played a role in Nemtsov's killing, also outlined what it said the war had cost Russia as well as the cost for the local regions hosting refugees from the East Ukraine war.

“It’s not a report with sensational information, it’s just a report so that Russian citizens can put everything together to understand the war in Ukraine and to make their own choice -- that’s what this report is intended to do,” said former prime minister Mikhail Kasyanov, who led the RPR-Parnas party with Nemtsov. “This report was prepared by Russian patriots. The war that Putin started with Ukraine contradicts Russia’s interests, it is harming Russia’s interests, and we will do everything we can to stop it,” said Yashin.

Nemtsov, who was a staunch opponent of Russian President Vladimir Putin, was shot dead on Feb. 27 while walking home with his girlfriend from a restaurant in Moscow, within steps of the Kremlin. Two men have been charged with his murder, but the person or group that ordered the assassination has not yet been named.

Speculation at the time was that his killing may have been ordered to prevent the release of the 65-page report which, Nemtsov had said, would show once and for all Russia’s involvement in East Ukraine.

After his death, investigators took his computer's hard drive and other materials, but his associates and fellow authors of the report were able to reconstruct evidence for its eventual publication. In addition to the online release, 2,000 copies were printed.

Over the last year a large number of media outlets, along with NATO and other Western officials had concluded that Russia was involved in assisting pro-Russian rebels in East Ukraine, a charge that the Kremlin has denied.

But Nemtsov sought to cut through the propoganda from both sides and wanted to present solid proof to the world.

While NATO produced satellite and picture evidence for Russian involvement, Nemtsov, claims the report, was able to put together his findings using public information from sources within the Russian government. He also interviewed Russian soldiers who had fought in the region, and the parents of those who had died.

"We gathered what we think is comprehensive proof of the presence of Russian troops," said Ilya Yashin, an opposition activist and one of the authors of the report. "All key military successes of the separatists were ensured by regular Russian army contingents."

The report said most of the interviewees, who were not named, had been paid 2 million rubles (about $40,000) and had been forced to sign a non-disclosure agreement promising not to discuss the deaths or their son’s involvement. Those who wanted to break the agreement were threatened with criminal prosecutions, claims the report.

While the number of deaths may have increased over the months since Nemtsov’s death, the report talks about two separate battles in which 220 soldiers died in total. The first 150 died in one battle in Aug. 2014. The Ukrainian army, according to the report, was on the offensive and was threatening to rout pro-Russian rebels, but Russian military involvement stopped Ukrainian government troops. A further 70 died while involved in the fight for Debaltseve, which continued through the signing of the Minsk II agreement and past the date when the ceasefire it instituted was due to go into force on Feb. 15.

According to the report, the Russian soldiers involved were officially dismissed from regular service in the Russian army and sent as volunteers to Donbas. While the Kremlin agreed that the soldiers were Russian, it also said that they were volunteers and had joined while on their own vacations and not on the order of the Kremlin.

But the costs to Russia have been more than just in hman lives, said the report.

It suggests that the military expenditure of the war is currently in excess of 53 billion rubles ($1 billion), with the costs of resettling refuges thought to be around 80 billion rubles ($1.5 billion).

But those costs pale in comparison to what people have lost in Crimea after it was annexed by Russia last year. Nemtsov’s report claims that around 2 trillion rubles ($39 billion) has been lost in salaries and around 750 billion ($14.9 billion) in savings.