The U.N. Security Council will hold a closed door meeting on Crimea Thursday, one year after Russia wrested the territory away from Ukraine, diplomats said.

Moscow, which claims it was forced to take over Crimea to protect ethnic Russians after the ouster of Ukraine's Kremlin-backed government, is refusing to attend the meeting, diplomats said on Wednesday.

Russian President Vladimir Putin on Wednesday triumphantly joined tens of thousands of supporters to mark one year since his takeover of Crimea, a seismic shift that shattered ties with Ukraine and the West.

Putin appeared on stage in front of a flag-waving crowd at a celebratory concert by the walls of the Kremlin to make an impassioned justification for seizing the Black Sea peninsula in a move that sent his poll ratings soaring.

Crises have a way of focusing minds. So it was with Eskander Budzhurov's 80-year-old mother when her son left the Crimean peninsula in a rush after it was annexed by Russia from Ukraine a year ago.

Budzhurov, a spry owner of a booth selling traditional Crimean Tatar snacks in Kiev, laughs as he recalls the mad dash to make his mother Skype-savvy before setting off with two sons for a new life, 800 kilometers (500 miles) away in the Ukrainian capital.

One third of Russian diplomats stationed at the embassy in Stockholm are spies, Sweden's intelligence agency Saepo said on Wednesday.

"Of the Russian embassy's diplomatic staff, about one-third of them are not actually diplomats, they are in fact intelligence officers," Saepo's chief counter-espionage analyst Wilhelm Unge told reporters as the agency presented its annual security report.

Russia on Wednesday signed a wide-ranging alliance with Georgia's breakaway region of South Ossetia that will further cement its control over the territory despite fierce condemnation from the West.

President Vladimir Putin inked a deal in Moscow with South Ossetian leader Leonid Tibilov that officially makes Russia responsible for defending the self-declared republic, where the Kremlin has stationed thousands of troops since a war with Georgia there in 2008.

Russia and pro-Moscow rebels on Wednesday condemned Ukraine for ratifying two bills on greater autonomy for the separatist east, saying they violated a peace deal and threatened a shaky month-long truce.

The latest wrangling over the east Ukraine peace plan came as Moscow celebrated one year since the annexation of Ukraine's Crimea peninsula, a key moment in the crisis that shattered ties with Kiev and the West.

NATO allies are scrambling to protect vulnerable Baltic partners from the threat of hybrid warfare, a Russian tactic that officials and experts say is based on deception rather than formal declaration of war.

Russian President Vladimir Putin's use of anonymous "little green men" to slice Crimea away from Ukraine last year sent alarm bells ringing throughout the three small Baltic NATO and EU members.

Greek Prime Minister Alexis Tsipras on Tuesday unveiled a surprise trip to Russia but also sought talks with European leaders to break a deadlock over reforms that has revived default fears.

The radical Greek government said Tsipras, who was already scheduled to visit Russia in May for its annual Victory Day parade, would now also travel to Moscow on April 8 to see Russian President Vladimir Putin.

Russia has stepped up military activity to pressure EU leaders who are set to consider fresh sanctions against Moscow, Polish Prime Minister Ewa Kopacz said Tuesday.

Russian President Vladimir Putin ordered massive military maneuvers on Monday, including the deployment of nearly 40,000 troops in the Arctic.

Russia's lower house of parliament on Tuesday refused to hold a minute's silence for murdered opposition activist Boris Nemtsov, with only two lawmakers standing in a show of respect.

Opposition lawmaker Dmitry Gudkov proposed that the lower house of the Duma hold a minute's silence at its first full session since the brazen assassination of one of President Vladimir Putin's most outspoken critics sent shockwaves around the world.