Ukraine is still welcome but not obliged to work with Russia on its post-Soviet Customs Union, seen as a potential counterweight to the European Union, President Vladimir Putin said on Thursday.

"We are not imposing anything on anyone, but if our (Ukrainian) friends want joint work (on the Customs Union) we are ready for a continuation of that work at expert level," Putin said in his annual address to the nation as pro-EU protests raged in Ukraine.

Spanish police said Wednesday they had arrested eight people on the holiday island of Majorca as part of an operation coordinated by Interpol against a Russian organized crime group.

The eight are suspected of laundering money for the Taganskaya criminal group, police said in a statement.

Russian Foreign Minister Sergei Lavrov urged all "responsible countries" to act to ensure a Syrian peace conference achieves positive results, in remarks during a visit to Iran on Wednesday.

Iran and Russia back President Bashar Assad's regime in the Syrian conflict, which is estimated to have killed almost 126,000 people since it erupted nearly three years ago.

Russian President Vladimir Putin on Tuesday paid tribute to Nelson Mandela, comparing him to Mahatma Gandhi and Soviet dissident and Nobel prize-winning author Alexander Solzhenitsyn.

"Without doubt he was a great friend of our people," Putin told reporters as he visited the South African embassy in Moscow to honor the memory of the anti-apartheid icon and Russia's "great friend."

Russian Foreign Minister Sergei Lavrov was due in Tehran Tuesday evening for talks that officials said would focus on bilateral ties, a landmark nuclear deal and plans for a Syria peace conference.

The two-day visit comes after Iran agreed in Geneva on November 24 to freeze or curb some of its controversial nuclear activities in return for limited relief from crippling international sanctions.

President Vladimir Putin ordered Russia's military on Tuesday to step up its presence in the Arctic after Canada signaled its intention to claim the North Pole and surrounding waters.

The tough and quick response to Canada's announcement reflected Russia's desire to protect its oil and natural gas interests in the pristine but energy-rich region amid competing claims there by countries that also include Norway and Denmark.

The European Union's top foreign policy official, Catherine Ashton, will travel to Ukraine on Tuesday for a two-day visit after hundreds of thousands of demonstrators protested against the rejection of an EU pact, the Commission said.

"She's expected to meet all the main stakeholders on both sides ... as well as civil society," a commission spokeswoman told a regular news briefing on Monday.

President Vladimir Putin Monday unleashed a wave of controversy in the Russian media world by naming a news anchorman notorious for his anti-opposition and anti-gay views to head a revamped state news agency.

Putin signed a decree dissolving Russia's biggest news agency RIA Novosti, ordering the creation in its place of a new media conglomerate.

Syrian opposition leader Ahmad Jarba said in Kuwait on Monday he would visit Russia at Moscow's invitation, but gave no date for the trip.

The announcement comes as Russia and the United States drum up support for their joint initiative to get all parties to the Syrian conflict to join peace talks slated for January 22 in Geneva.

United Nations Secretary-General Ban Ki-moon called Ukrainian President Viktor Yanukovych on Sunday to urge for dialogue with his rivals as large-scale protests gripped Kiev, the U.N. said.

A U.N. statement said Ban "expressed his grave concern about the situation in Ukraine, emphasized that there must be no resort to violence and appealed for peaceful dialogue among all parties concerned."