Ultra Orthodox Jewish men watch a bonfire during the Jewish holiday of Lag Ba-Omer in Jerusalem's Mea Shearim neighbourhood April 27, 2013. Israelis celebrate the Jewish holiday of Lag Ba-Omer, which marks the end of a plague in the Middle Ages that killed thousands of disciples of a revered rabbi in the holy land, by lighting bonfires across the country. (Photo by Ronen Zvulun/Reuters)

Nadezhda Tolokonnikova, a member of the feminist punk band, p*ssy Riot, right, reads papers at a district court in Zubova Polyana 440 km southeast of Moscow in Russia's province of Mordovia, Friday, April 26, 2013. A Russian court is to consider whether one of the jailed p*ssy Riot members is eligible for early release. Nadezhda Tolokonnikova, in custody since her arrest in March 2012, is serving a two-year sentence for the band's irreverent protest against President Vladimir Putin in Moscow's main cathedral. Tolokonnikova's lawyer Irina Khrunova is at right. (Photo by Mikhail Metzel/AP Photo)

A guard stands at Dityatki checkpoint, marking a 30 km (18-mile) zone around the Chernobyl nuclear power plant April 23, 2013. Ukraine will mark the 27th anniversary of the Chernobyl disaster, the world's worst civil nuclear accident, on April 26. (Photo by Gleb Garanich/Reuters)

In this photo taken on Friday, March 15, 2013, members of a pro-Kremlin youth group attack pushers of spice, a synthetic drug, in Moscow, Russia. Russian officials and anti-drugs campaigners say that spice has become one of the most dangerous drugs widely available to youngsters and almost impossible to ban because of the constantly changing chemical ingredients. (Photo by Alexander Zemlianichenko Jr/AP Photo)

A life-size interactive inflatable sculpture of Stonehenge called “Sacrilege 2012” by English contemporary artist Jeremy Deller on display as part of the “Inflation!” exhibition curated by Mobile M + on April 24, 2013 in Hong Kong. The inflatable artwork is one of six on display as part of the exhibition which is open from April 25, 2013 until June 9, 2013. (Photo by Jessica Hromas)

A schoolgirl collects rubbish from Karachi's Clifton beach early morning April 22, 2013, during a cleaning campaign as part of the commemoration of Earth Day. (Photo by Akhtar Soomro/Reuters)

Maria, 18, wearing a traditional Sevillana outfit, poses for a portrait during the traditional Feria de Abril (April fair) in the Andalusian capital of Seville April 16, 2013. (Photo by Marcelo del Pozo/Reuters)