MOSCOW -- Russian Prime Minister Dmitry Medvedev has long styled himself as a liberal-leaning lawyer who loathes corruption, having launched an initiative to combat rampant graft in 2008 -- one of his first acts as president during his four-year stint in the Kremlin.

But now Medvedev is taking fresh fire on the issue from opposition leader Aleksei Navalny, who is accusing the former president of being one of Russia's richest men and one of its "most corrupt" bureaucrats.

In Navalny's latest investigation, released online on March 2 and delivered in his trademark caustic style, the Kremlin opponent accuses Medvedev of using an array of charity and nonprofit organizations to collect donations from oligarchs and state banks and then redirecting the funds to purchase pricey assets.

Navalny called these donations naked bribes. "The only recipients of this 'help' are Medvedev and his family," he said.

The report, accompanied by an explanatory video, alleges that at least 70 billion rubles ($1.2 billion) in funds and assets have been transferred to organizations controlled by people close to Medvedev. It claims that this alleged empire includes palaces, elite residences, estates, yachts, and vineyards in Russia and abroad.

"The real owner of the assets is almost impossible to trace because by being registered to charity foundations, they essentially belong to no one. Medvedev's property is managed by his friends, schoolmates, and trusted people," Navalny alleges in the investigation.

He called Medvedev "one of the richest people in the country and one of the most corrupt bureaucrats."

The investigation was quickly dismissed by Medvedev's office as political bluster and "propaganda."

'Nothing To Do With Charity'

Citing public property records, the investigation alleges that Alisher Usmanov, a billionaire with deep connections in Russia's ruling elite, donated a property in the wealthy Rublyovka village outside Moscow worth 5 billion rubles ($85 million) to a nonprofit fund for state social projects reportedly led by two former university classmates of Medvedev.

"This fund has nothing to do with charity," Navalny said.

Usmanov had not responded publicly to the report as of March 2, and the respected Russian daily RBK reported that his company, Metalloinvest, declined to comment when reached by the newspaper.

The investigation did not uncover any assets linked on paper to Medvedev. Navalny alleges that the organizations cited in the report are managed by people close to Medvedev who oversee "personal" property for the prime minister.

Navalny drew attention to properties that include a vineyard in the Black Sea town of Anapa and one in Italy's Tuscany region; a residence in the western Kursk region; a dacha in the central Ivanovo region investigated by Navalny in September; an estate in Rublyokva; a house in Krasnaya Polyana near Sochi; a house in St. Petersburg; and two plots of land on the Black Sea.

The investigation comes as Navalny tries to raise his profile in order to take part in the 2018 presidential election despite his conviction last month on embezzlement charges that he and his followers say were trumped up to eliminate him from the race.

Medvedev's spokeswoman, Natalya Timakova, said on March 2 that the investigation looked "distinctly like election campaigning" and that commenting on "propaganda attacks" by a convicted man was "pointless," the Interfax news agency reported.

The allegations were reported in several influential newspapers and online news portals, but were ignored by most pro-Kremlin media. As the investigation circulated widely on social media, state news agencies on March 2 reported Medvedev's message of support to farmers that the trade embargo on European Union produce is here to stay.

Navalny rose to prominence during antigovernment protests over allegations of parliamentary election fraud in 2011, and he has emerged as the de facto opposition leader. He carved out an online following as a slick social-media operator and by harrying President Vladimir Putin's allies, whom he has accused of corruption in a series of hard-hitting investigations.

In December, Navalny announced his bid to run for president next year, although the authorities consider him to be barred from the race after he received a suspended sentence last month. He has said he intends to run anyway and has been drawing attention by opening regional election-campaign offices.

A recent poll by the independent Levada Center found that the percentage of Russians prepared to vote for Navalny had fallen from 33 percent in 2011 to around 10 percent this year.

In liberal opposition circles, reactions to the investigation ranged from praise to downbeat skepticism

Roman Dobrokhotov, a journalist and former opposition activist, suggested the investigation might indeed land a blow to Medvedev, but that it could lead to him getting replaced by someone with a tougher reputation, such as Putin's longtime close associate, Rosneft CEO Igor Sechin.

"Now Putin is like: Medvedev has lost my trust, I'll replace him with Sechin. Enjoy," Dobrokhotov wrote on Twitter.