Russian President Vladimir Putin has warned European leaders that Ukraine's delays in paying for Russian gas have created a critical situation. Pipelines transiting Ukraine deliver Russian gas to several European Union countries and there are fears that the current tensions could trigger gas shortages.Pro-Russian separatists are holed up in official buildings in Donetsk and Luhansk, eastern Ukraine. Meanwhile, a European human rights body has stripped Russia of voting rights. The Parliamentary Assembly of the Council of Europe monitors human rights in 47 member states, including Russia and Ukraine.