Russia on Thursday dismissed as absurd Kiev's claims that it had shot down a Ukrainian warplane over its territory, a move that led to a fresh spike in tensions between the two ex-Soviet states.

"This is absurd, just like all previous accusations against the Russian defense ministry by Kiev authorities," an unidentified high-ranking representative of the defense ministry told the Interfax news agency.

President Vladimir Putin denied on Thursday Russia plans to reopen a Cold War listening post in Cuba as new U.S. sanctions over Ukraine ratcheted up tensions between Washington and Moscow.

Russian broadsheet Kommersant, citing several official sources, reported on Wednesday that Moscow and Havana had agreed in principle to reopen the Lourdes spy base during Putin's visit to the Communist-run island last week.

Italy reacted with disbelief on Thursday to charges that Italian Foreign Minister Federica Mogherini would be too pro-Russian as the European Union's next foreign policy chief because of Italy's economic ties with Moscow.

"Italy is hardly the only country that does business with Moscow and that does not want Moscow to turn against it," said Giampiero Gramaglia, a columnist and spokesman for the Istituto Affari Internazionali think tank in Rome.

Eighteen Ukrainians with shrapnel wounds were hospitalized in Russia after fleeing from the conflict-torn east of their country, the health ministry said Thursday, adding that one has died.

Russian media reported that the Ukrainians drove up to two border posts Wednesday waving white flags and asked to be let in for medical treatment.

The U.S. and EU bolstered sanctions against Russia over its alleged support of separatists in Ukraine, drawing an angry rebuke on Thursday from Moscow which said the measures amounted to "blackmail".

President Barack Obama in sanctions imposed Wednesday took his first direct swipes at the Russian economy's finance, military and energy sectors, further escalating the worst standoff between the Kremlin and the West since the Cold War.

Rebel leaders in eastern Ukraine will hold a videoconference Thursday with a group of mediators to discuss talks on a possible truce, a top separatist chief said Wednesday.

Plans for similar Internet negotiations between the separatists and a trilateral Contact Group involving representatives of Ukraine, Russia and the OSCE fell through Tuesday leading negotiators to slam the rebels for not being committed to talks.

The number of deaths from AIDS is going up in Russia, contrary to a global downward trend, a senior Russian health official said Wednesday, blaming a lack of public education about HIV infection.

"Last year we registered 22,000 AIDS-related deaths, against 20,000 the year before," the head of the Russian Federal Agency against AIDS, Vadim Pokrovsky, told Agence France Presse.

Thousands of Russians on Wednesday paid their last respects to radical opposition politician Valeria Novodvorskaya, who dedicated her life to fighting first the Soviet authorities and then President Vladimir Putin.

Both ordinary and prominent Russians, many clutching flowers, turned out in central Moscow to pay tribute to the fiery Soviet-era dissident, who died aged 64 on Saturday.

When young mother Natasha woke up to find her quiet suburb suddenly on the frontline of fighting between Ukrainian troops and pro-Moscow rebels -- she knew it was time to pack up her three kids and get out.

Now they're waiting anxiously in line with over a hundred others, mainly women, children and elderly from around the main rebel-held city of Donetsk for a bus put on by the separatist authorities to ferry them across the border to Russia.

Russian actions to resolve the Ukraine conflict have been insufficient so far, a German government spokesman said Wednesday ahead of an EU summit that will consider fresh sanctions against Moscow.

German Chancellor Angela Merkel and Ukraine President Petro Poroshenko had agreed in a phone call Tuesday that "Russia has been insufficient in meeting expectations" on steps to end the fighting between government forces and pro-Russian separatists, said Merkel's spokesman.