The best photos from the international wire agencies as chosen by our picture editors

The treaty organisation has traditionally focussed on the threat of Russia, but is increasingly concerned about China’s nuclear arsenal and lack of transparency.

Experts believe the snow algae may be a marker of climate change but also that their rise could hasten the shrinking of glaciers and snow caps.

The largest diamond ever cut in Russia - a 100.94 carat stone called the Alrosa Spectacle - will be auctioned in Geneva later this month.

The Commonwealth Heads of Government meeting that was scheduled to be held in Rwanda in June has been postponed, despite urgings by Australia and Britain that the conference should not be delayed for a second time.