Russian President Vladimir Putin on Wednesday congratulated Barack Obama with his victory in a tightly-fought U.S. presidential election vote that was greeted with relief in Moscow.

The Kremlin said Putin had reacted "positively" to Obama's victory over Mitt Romney after a campaign that saw the Republican Party challenger refer to Moscow as Washington's chief geopolitical foe.

Russian President Vladimir Putin Tuesday fired defense minister Anatoly Serdyukov over a corruption scandal, the most dramatic change to the government since he returned to the Kremlin for a third term.

Putin replaced Serdyukov, who had been implementing an unpopular but Kremlin-backed military reform, with Moscow region governor and long-standing ally Sergei Shoigu, his spokesman said.

Several thousand Russian ultra-nationalists whose ranks included fierce Kremlin critics marched through central Moscow on Sunday calling for President Vladimir Putin's resignation and an end to illegal immigration.

Armed with anti-Putin slogans and black and yellow flags of pre-revolutionary Russia, the black-clad participants in the "Russian March" took to the streets as Putin is facing the most vocal opposition to his rule since he came to power 12 years ago.

Ukraine's security service said Friday it was conducting a formal check into the disappearance of a Russian opposition activist who claimed to have been abducted from Ukraine by Russian agents.

The Security Service of Ukraine (SBU) said in a statement that it was looking into the "urgent departure" of Leonid Razvozzhayev, who is now in a Moscow prison after being charged with plotting mass riots.

Russian deputy Foreign Minister Mikhail Bogdanov arrived in Tehran on Monday to discuss the crisis in mutual ally Syria with Iranian officials, Fars news agency reported.

"Mikhail Bogdanov, deputy foreign minister for Middle East and President Vladimir Putin's special representative arrived in Tehran at the invitation of his counterpart Hossein Amir Abdolahian to discuss regional issues and Syria," Fars said.

Russia's President Vladimir Putin on Wednesday defended its arms trade against criticisms over its dealings with Syria, insisting only the United Nations could dictate restrictions on arms sales.

Putin defended Russia's right to trade weapons with whomever it wanted, without mentioning Syria but in an apparent reaction to recent attacks from the West over supplies to Syrian President Bashar Assad's regime.

Russia on Tuesday urged the West not to "search for pretexts" in order to conduct direct operations in Syria while also calling on Damascus and Ankara to exercise restraint along their flashpoint border.

"In our contacts with NATO partners... we call upon them not to search for pretexts to carry out a military scenario or initiatives like humanitarian corridors and buffer zones," Deputy Foreign Minister Gennady Gatilov told the Interfax news agency.

Vladimir Putin has sent a Black Russian Terrier puppy to his Venezuelan counterpart Hugo Chavez, who joked the Russian strongman would receive a capybara, the world's largest rodent, in return.

The three-month-old puppy was given to Chavez by Igor Sechin, one of Putin's most trusted lieutenants and chief executive of Rosneft, Russia's largest oil company.

Russian President Vladimir Putin on Thursday accused the West of pursuing policies that had destabilized states in the Arab world and now risked creating chaos in Syria.

"The most important thing is that our partners cannot stop themselves," news agencies quoted Putin as saying at his local Moscow residence at a meeting with local residents of the Ryazan region in central Russia.

Russian President Vladimir Putin said Wednesday world powers should draw lessons from their mistakes and stop interfering in crisis-hit nations of North Africa and the Middle East.

Putin did not address the raging conflict in Syria directly and appeared to be referring to the overall threat of the use of force that has also been applied by Israel and the United States to Iran over its nuclear program.