Top U.S. officials raised broad and specific concerns about Russia's legal environment after the conviction on Monday of one-time oil magnate Mikhail Khodorkovsky and his associate Platon Lebedev.

We are troubled by the allegations of serious due process violations, and what appears to be an abusive use of the legal system for improper ends, White House spokesman Robert Gibbs said in a statement on Monday.

Secretary of State Hillary Clinton said the pair's second conviction on charges of embezzlement and money laundering raises serious questions about selective prosecution - and about the rule of law being overshadowed by political considerations.

Khodorkovsky - who was once the richest man in Russia and ran the major oil company Yukos - was convicted along with Lebedev in 2005 of not paying all taxes due from profits at the company. The former oil baron is currently serving an eight year sentence. Khodorkovsky had previously financed opposition political parties in Russia. Current Prime Minister Vladimir Putin ordered prosecution of Khordokovsky when he was still President. 

In the latest case, Khodorkovsky was accused of embezzling oil worth $25 billion from investors. A sentence has not yet been announced for the most recent conviction.

Gibbs said that the apparent selective application of the law to both defendants undermines Russia's reputation as a country committed to deepening the rule of law.

The Russian Foreign Ministry said in a statement on Tuesday that parties within and outside Russia should mind their own business, saying attempts to put pressure on the proceedings were unacceptable.

This and similar cases have a negative impact on Russia's reputation for fulfilling its international human rights obligations and improving its investment climate, Clinton said.

Both officials expressed partial support for Russia's government.

The Obama administration stands in solidarity with the many people in the Russian government, in the legal system, and in civil society who are committed to strengthening the rule of law and deepening the commitment to universal values enshrined in the Russian constitution, Gibbs said.

He said President Obama had spoken about this case and others with Russian President Dmitry Medvedeve as part of their ongoing conversation about President Medvedev's important campaign to strengthen the rule of law and modernize Russia's political and economic system.

Clinton also said she welcomed Medvedev's plans.

[B]ut their fulfillment requires the development of a climate where due process and judicial independence are respected, she said.

Both officials said they would monitor appeals by the defendants.