The editor of an independent investigative Russian newspaper claims to possess a top secret document that proves the Kremlin planned an invasion of Ukraine last year.

Dmitry Muratov, the editor-in-chief of _Novaya Gazeta, _told a local radio station he has a strategy paper that purportedly shows Moscow began plotting an incursion in Ukraine sometime between February 4 and 15, 2014, when the document was allegedly drafted. The dates coincide with the protest-filled weeks leading up to the collapse of the Ukrainian government and the ouster of former President Viktor Yanukovych, a Russian ally, on February 22.

Muratov revealed nothing about how the leaked document found its way to the newspaper, but told Moscow radio station Ekho Moskvy he is confident about its authenticity. He said he would release the document this week.

If proved to be a bona fide Kremlin-authored document, the information in it would directly contradict President Vladimir Putin's repeated assertions that Russia has had nothing to do with the separatist uprising in Ukraine and that his country's troops have never entered Ukrainian territory.

Instead, Muratov claims the document reveals the Kremlin felt it had to intervene in Ukraine's escalating political crisis so that it could retain a primary market for Russian natural gas and continue to funnel gas to Western Europe through Ukrainian pipelines.

Ukrainian demonstrators sought closer economic ties to Europe during the deadly Euromaidan protests that led to Yanukovych's downfall. A break with Moscow could have portended a serious hit to the stability of Russia's economy, which has nonetheless suffered significantly in the wake of crippling Western sanctions enacted in response to Russia's role in Ukraine.

Russia's strategy, as outlined in the document, reportedly included invasion plans that would begin with a "main thrust" in "Crimea and the Kharkhiv region," and ultimately lead to "the annexation of the eastern regions," Muratov said.

According to Muratov, the strategy paper also characterized Yanukovych as "a person without morals and willpower whose downfall must be expected at any moment."

_Novaya Gazeta _is recognized internationally as a leading Russian newspaper that produces tough investigative reports on government corruption. It is a nominee for the 2015 Nobel Peace Prize, and one of few independent outlets critical of the Kremlin. As a result, the paper's reporters have been targeted with violence, with six _Novaya Gazeta _journalists killed within the last 15 years.

Pro-Russia separatists in the country's east have battled Kiev's army since April. Several ceasefires brokered by foreign powers have failed to put an end to the conflict. Hopes for a new truce that began last Sunday quickly faded after separatist troops took Debaltseve, a strategic railway hub, on Wednesday.

The West and Kiev have continually accused Moscow of arming and training the separatists, but Russia maintains the insurgents are acting independently.

Meanwhile, military and civilian casualties in the conflict continue to mount. At least 5,600 people have been killed in Ukraine since the fighting began 10 months ago, according to the United nations.