As negotiations over the crisis in Ukraine begin in Geneva, tension is rising in the Ukrainian east after security forces killed three pro-Russian protesters, wounded 13 and took 63 captive in the city of Mariupol. Ukrainian officials said the pro-Russian separatists had attempted to storm a military base. The killings came just after the unraveling of a Ukrainian operation to retake government buildings from pro-Russian separatists. Earlier today, Russian President Vladimir Putin accused the authorities in Kiev of plunging the country into an "abyss" and refused to rule out sending forces into Ukraine. Meanwhile, NATO Secretary General Anders Fogh Rasmussen has announced a series of steps to reinforce its presence in eastern Europe. "We will have more planes in the air, more ships on the water and more readiness on the land," Rasmussen said.